It was that easy for me. But I don't have everything online. Took me a few goes at it to realise that if you set it scraping from the top level directory where your media is stored as:
Lost/
Lost/Season1
Lost/Season1/Lost (s01e01).avi
Lost/Season1/Lost (s01e02).avi etc etc
Lost/Season2/
Lost/Season2/Lost (s02e02).avi etc etc
It worked fine. If it doesn't know what show it is you can select "manual" and tell it.
Guess how well it works depends on how your collection is structured. Took me about an hour to get all my data done but like I said I don't have everything online. Once it's done and knows the content of each directory you can set it to auto scan on startup to catch any new additions. It's very impressive.
The other sweet thing is that it keeps track of what you've watched and what you haven't when in library mode so no more coming back after a few days and watching the first few minutes of 10 episodes trying to find the one you haven't seen!
The only media I've had trouble with are real DVD's. A couple caused a crash but the later svn versions seem to have that problem solved.
The next couple of months of bug chasing should see an end to any stability issues for the current feature set (which is comprehensive already).
It's great that it's so feature complete already given the relatively short time they've been developing for other platforms besides the original xbox and for the vast majority of things I use it for it's been very stable.
The executable comes in at 88MB! Everything included. Even the MCE remote works out of the box

Add some 3rd party skins and your good to go.
I've had to tweak a couple of things. Changes the preview/skip buttons on the remote to work same as MCE including a 30 sec forward 8 sec back just etc. Everything is well documented on how to do advance configuration in advancedsettings.xml.
I've also got two user profiles set up. The first is a "Mum and Dad" profile that has all the adult content in it and is pin number protected. The second is the "Kids" that doesn't require a pin but only gives them access to their shows and movies. A feature inexcusably lacking in MCE.
Cheers,
Arkay.