Seriously. I get it alright.

The arguments of alternatives have been closed off and the discussion about "That other OS" is now progressing in the appropriate forum where you can choose to participate or not.
It would appear that I can't say much at the moment without taking a torrent of abuse but I've been comparing performances of operating systems, all of them. Having used a number of other OS's in recent times (including Apple and XP) I don't believe it's accurate to argue the performance of Vista when talking in isolation about Windows only OS's. XP performs better on the same spec machine that Vista requires, but it's a 10 year old OS. You can't compare Vista to XP and get a valid comparison unless your basis of comparison is that you didn't get anything better out of Vista than you already had in XP, and that is the criteria most people have applied. Most people have also upgraded their hardware to get a similar level of functionality as they had previously.
The press you see coming out of MS lists a lighter OS with better performance as a design goal for Windows 7. If they didn't have an issue with Vista there would be nothing to fix with Windows 7.
From a media center perspective there is the unsolved issue stopping many people from playing a dvd. That again is unknown, appears to be random, may or may not be DRM related. Who knows but when every second DVD won't play in a media center machine it's frustrating.
There are things about Vista that are plainly bad in my opinion. The interface is an unnecessary deviation from XP, so much so that the initial reaction from most was negative. Particularly those that use office on a regular basis and it's a lot of effort to re-learn the interface for no apparent perceived gain. Just working out how to turn the file menu back on in IE can be a hair tearing experience.
Mapping and using network drives between XP and Vista is an exercise in futility and un-necessarily complicated for a function that should just work. Vista to Vista is fine but I'm not about to go upgrade everything to Vista so I can easily share files.
The recent changes with Fiji to a completely different recording format cannot be justified by the need to house more metadata and provide a more rich content experience (as MS has tried to justify it by), there's a perfectly good WMP database in the background that could do that. That change alone breaks a lot of commercial tools that people use and a lot of open source ones as well that at the least will be an extended inconvenience and at worst will require money to be spent to replace them as new tools or upgrades emerge to address that change.
I've been hearing about a richer media experience for years now and still do not see anything interesting in what Vista presents me with regard to my recorded TV and with DVD's and avi files the content richness is even poorer. Without 3rd party add ons you can't even have a description of an online media file and the plugin interface still does not feel integrated.
Format support is limited. You have to install codec packs etc in order to add support for other formats and often that means breaking a previously working format. Negotiating Windows directshow codec priorities is difficult at best and getting a machine that works correctly with your matroska videos and your AAC audio can be incredibly hard for a novice and difficult for the experienced.
On several occasions I had my Vista MCE machine stop functioning, requiring a re-build from Acronis image. There was no explanation. It was just in an endless BSOD/reboot cycle. I couldn't even get in far enough to fix it. Even after one of those re-installs from a perfect acronis image the machine came up telling me the video driver currently installed wasn't written for this version of the OS? The only thing different to when I took the image was the date.
Standby/resume would be working fine and one day just stop until you re-set all the settings and got it working again. Settings would seemingly change or be forgotten.
The layout of the folders in explorer is complex and overly verbose and doesn't seem to follow any logical pattern. The way MCE adds in a lot of media folders that you never asked for is annoying and shouldn't be required and the procedure to remove them is longwinded and not at all obvious.
UAC was a pointless excercise. Like you can make the end user responsible for the security of the OS by making them "agree" to every little change they want to make. No one can live with it for more than half an hour but by turning it off you are made responsible for circumventing the provided security. We often discuss the average Joe. How could the average Joe know enough about computers to know whether it's ok to press allow or deny given the highly technical nature of most of the questions UAC proposes? It's very un-userfriendly.
Thumbnails as discussed have been a major issue to this day. There's no easy way to write protect your shares (or turn off the delete mechanism in MCE to protect your media from the kids and accidental deletion). If you do write protect the shares the thumbnail generation goes out the window and takes forever as the ehthumbs_vista.db can't be written to the share. It never should be written to the share. It should be stored in a local DB. Vista will happily modify your media without your permission if you don't write protect the data. mp3 albums are a prime example and the manner in which it expects the files to be tagged (ID3 album artist), goes against a very large percentage of the way any other mp3 player/tool works leaving you to re-tag your entire collection just to suit MCE rather than MCE supporting a more generic ID3 tagging structure.
MCE is inconsistent. It will happily use the WMP database to index the video folders that it adds unnecessarily to your collection views but it stores the thumbnails in the share folders.
Vista added nothing with regard to repeatedly asked for functionality such as parental control (something that is very important to those with young children), the ability to ff/rew avi files should not be an external community add on etc, I could go on, there are many many more missing basic features like more than 2 tuners (which may now have been implemented in Fiji, as long as you're prepared to go buy it with enough hardware to justify and OEM purchase).
Fiji also still ignores repeated requests for some basic user friendliness and many of those things are not difficult to implement. It just sometimes seems that the decision makers are not interested in addressing user desires.
Often we realise that there are legal issues and bureaucratic issues behind these decisions but that doesn't help me as an end user wanting a product that works in a particular way.
Remote control "lag" got worse with Vista, trying to scroll across a large video library can be very unattractive when the highlighted icon sticks for a few seconds then jumps madly across (with an associated burst of sound), when there seem to be some free cycles to handle the animation.
For no apparent reason when I began recording "Friends" for my wife every recording exhibited stutter, right through the entire episode. It appeared at the time that this was caused by excessive disk thrashing on wakeup which continues on through the recording if the recording started before the disk settled. Even though indexing etc had been switched off. All other recordings were perfect as the machine had been on long enough for the excessive disk thrashing (whatever it is that causes it), had time to settle. No matter what I did, trying to set it to wake up a lot earlier than it needed to for the disk activity to settle never fixed the issue and I never found a solution.
Whatever Vista is doing in the background I don't trust the fact that I can see and hear it's busy yet no tool in the OS actually reports what is causing the activity. Nothing in the system monitor. Task manager says nothing is going on, yet hammer away it will.
As vlad mentioned with the video driver issue, whomever you attribute that to. They still are not as stable or functional as those in XP. With Windows 7 on the horizon and Vista not being up to scratch (even now for some things), that's a large part of the lifetime of Vista that it's not been as usable or efficient as XP was provided you spent the time to hack at XP to get it stable (and that took a fair bit of work after setup). Vista is certainly better and easier on setup but I see that more as a factor of all the patches and updates being included in the install disk rather than having to be applied after install. I certainly didn't find it that much more stable than XP.
Even now the video drivers exhibit errors, crash periodically, black levels are often out of whack, de-interlacing issues are common etc. Apart from the change in interface very little from a usability and "feel" standpoint changed.
The networking issues of Vista (and the time it took to fix) were also, in my opinion, unacceptable for a release version of any OS. Yes you can argue that any new OS has teething issues but the network stack shouldn't be one of them and it shouldn't take months and months to fix, maybe days after the fault is identified. It's a core component. If it were some new feature such as the oft discussed never implemented DBFS that was causing issues then you could understand. But a malfunctioning network (even if fixed now), was beyond my personal level of tolerance for a commercial product.
These are my experiences and I've been involved with Vista since the beta program began 12 months prior to it's release.
Please don't view it as me ragging on MS, or bagging Vista. Just trying to say what I've experienced and why I was not happy with Vista and that is only from an MCE perspective. There has been other issues with it from a general desktop OS perspective that I have read about but haven't experienced and as such won't comment on.
Vista's uptake and reception by the general community is testament enough to how it was received. You can say that's due to sentiment rather than actual use and perhaps some of it is, but I seriously doubt it all is.
Vista was supposed to have been re-written from the ground up with security in mind yet you seem to need just as much 3rd party virus and malware protections as you did in XP.
To me I believe Vista shouldn't have been released when it was, it was (and potentially still is) not ready from my perspective, but that is just my opinion so please don't take offence to my comments.
I don't intend to respond further to this thread but felt it necessary to let people like Slimf try to understand why I feel the way I do.
To sum up why Vista failed me all I can say is "Vista MCE failed to welcome me as a user".
Cheers,
Arkay.