I've been using a Mini as my home PVR, DVD and general media player for a year now, and I've been very pleased with it. There are a few issues:
*EyeTV (the most commonly used PVR software) is rubbish, for reasons that have been discussed on El Reg in the past
*Matroska (.mkv) files won't play cleanly in FrontRow - although the guys working on Perian (www.perian.org) are doing a great job at trying to fix that.
*No Windows-DRM support for things like 4OD - although the PVR catches everything I want to watch on real TV.
..but aside from these the hardware is excellent. With more effort on the software it could easily be a Sky + beating package without a subscription charge. None of this is going to earn Jobs a dime though, so I can understand why its being dropped..