PS3 media centre has actually stopped me from buying a popcorn hour it is that good, sure i miss some stuff from the pch but its a solid product
It's only problem is that while it handles all the usual containers (mkv etc), if it has to transcode the video in it @ 1080p, it can't do it properly, you either need a powerhouse of a processor (Q6600 @ 3.2Ghz) and then the results are pretty poor (lots of artefacts).
If the MKV already contains VC-1/AVCHD video then it works really well..
We set this up at my brothers last weekend, as he thought he could replace his A110, but alas, about 20% of his media didn't work properly, and some of the transcodes looked very bad on his Plasma and PJ.
Interestingly, this weekend, he borrowed a WDTV HD box (£84) which has the same processor as the A110 in it, and that played everything flawlessly, instant on, just plug in any USB HDD and off you go, it even handled full bitrate m2ts blu-ray files.
We flashed the alternate firmware, plugged in a usb-ethernet adapter, and it then streamed over the network.. for £84 that could knock the Popcorn hour out of the weeds, and if you have a varied/problematic media collection, the WDTV HD is a very low power, no-nonsense, plays all device that you can just plug a USB HDD into, so no PC required.