The trouble with using a MCE spec card in a non-MCE intall of XP is that they don't usually ship them with software and a remote. I've just got one for my MCE machine and it came with nothing, just a free anti-static bag.
I am used to Tivo, so the MCE interface is pretty crap for PVR functions, but I have seen andym's MythTV setup and it's pretty impressive (although still a little buggy I think?) I can't speak for any other interface, but I imagine they are all pretty much as crap as each other.
Why don't Tivo do MCE type thing for PC's? (or even better macs!)
Cheers
Cris.