I have to admit I have not so far experienced this irratic mouse issue being described.
I'm using the MCE keyboard as I write this reply and while I had to get used to the concept of applying pressure to the mouse to move it, I'm finding that I can move the mouse quickly or slowly using the standard mouse speed setting (ie: Windows default) without any problems. I'm finding it reasonably precise, although not as exact as using a normal mouse, but it's no more annoying than the nipple mouse on a notebook. I use it by smothering the nipple with the mid-section of my thumb behind where my thumbnail stops and move my thumb about by rocking it - I don't use the tip of my thumb. I find this gives me a lot of control.
My mouse is definitely not jumping about. Even my girlfriend finds it reasonably simple to use - in fact, she liked it a lot.
Probably the biggest thing I'm enjoying is the range. I'm sitting on my couch about 4 metres away from my HTPC that sits on the side of the wall that my projector projects on, but also worked from 8 metres back, although the mouse movement was a bit harder to do from that distance, and this may well be the erratic mouse issue others are claiming to experience. The keyboard works from pretty much any angle, but the mouse only can be used when the receiver is less than 90 degrees angle from the keyboard.
I am using the most recent eHome receiver update from the Windows Update website (which appears to be the one and only update that was released as previously described).
Probably the only complaint I could level against this keyboard is the learning function - it's bloody finicky and took me about 15 minutes of repeated learning before the keyboard finally accepted my amp's volume signals. I have yet to get it to accept my TV power button signal.
The keyboard lock is a bit silly - it's just a power switch! The keyboard is completely unresponsive in lock mode. It'd be handy if the activity LED would flash or something to advertise "I'm locked" - it'd drink up bugger-all battery.
All in all, I'm finding this keyboard to be excellent overall. A simple and useful product and worth the purchase. Highly recommended. My old Microsoft RF wireless mouse and keyboard have been retired.
