What you have is PowerDVD 7.3 Ultra (OEM version). Ultra refers to the fact that it can play BD/HD DVD movies. What you have to pay for is PowerDVD 7.3 Ultra (Retail Version). The difference is mostly in how they handle audio tracks. By default, the OEM version will try to downmix the HD audio tracks to 2.0 channels, although on mine I have achieved the following (PowerDVD output -> What amplifier gets):
LPCM -> Dolby Digital Surround EX (Ultraviolet, POTC:AWE)
Dolby TrueHD -> Dolby Digital 5.1 (Troy DC)
DTS-HD -> DTS ES Discrete 6.1 (Stargate)
Dolby Digital Plus -> Dolby Digital Surround EX (Transformers)
That DTS track on Stargate was by far the best sounding movie I have run through my home theater to date!
Bear in mind, my amplifier is a 4 year old Pioneer VSX-815K. It doesn't natively understand PCM, TrueHD, DTS-HD, Master Audio, any of those. I think it sounds pretty darn good!
With that said, at this point there is no need to any bigger on the amp for those audio tracks since there is no sound card yet made that can decode them natively. You have to depend on the software (PowerDVD) and send them out the analog jacks. Haven't tried this with the OEM version yet, so I don't know how well it would work.
Basically, to distill that novel down, if you have a decent amp, the OEM version will do you admirably well. I see no reason at this point to buy the retail version, for the following reasons:
PowerDVD quirkiness (ringing tone on DTS resample)
Lack of soundcard support
Other offerings pending (Arcsoft, WinDVD, Nero)
Buy-in price (TrueHD/DTS-HD amps can run several hundred dollars)
To answer your question on MCE and remote integration, check Post #58
to this very thread.