I've now finally got around to installing Windows MCE on my media centre after fooling around with Media Portal as my media centre software.
My media centre is based on a cheap AOpen XC-Cube with a cheapo Sempron 2600+. Amazingly it works pretty well the only problem being the transition animations are not too smooth occasionally when running at the highest possible resolution (1280x1024x32bpp).
I've been quite impressed with the software. It is much smoother to set up then the open-source ones I have used in the past, but I don't particularly want to use something because it is the path of least resistance.
In general the smooth set up and the smooth operation has been better than I expected. It now works much better with the MCE infra-red keyboard and control, the stand-by operation is much smoother and wake-up ability much better. Maybe the drivers installed for MCE since it does not necessarily use the same drivers as XP Home/Pro make it more stable?
Still after installing it you have to download one round of updates, then 78 updates, then another 13 (at least). That takes ages - yawn.
I'm actually quite impressed by the associated operating system - it is XP with a lick of paint and extra features. I have no idea why Microsoft didn't use it as an opportunity to release a new version of the OS at the consumer level since MCE is only really for manufacturers. All manufacturers seem to be using MCE ahead of XP Home anyway now.
Overall it has been a very good experience and my wife is finding it easy to use, that is always a good yardstick.
