Well, now I think I'm leaning toward the PS3 over the S550/560. The PS3 will maintain its value for much longer, while standalones will continue to plumet in price every year. The S550 is selling for $400 now, but it's successor, the 560 will be $350 but won't be available for another 3 months.
I managed to get in on a Sony Card special, so I'll get $200 off any purchase from Sonystyle and right now Sony is offering free shipping and a free 2nd controller ($55 value). So my total cost would be $199 for an 80GB PS3 with two controllers. For that price, I think I can deal with the slight disadvantage in features. The biggest pain will be that the AVR I am going to purchase (H/K 254) cranks the LFE channel on PCM input, which means that every time I use the PS3, I'll have to fiddle with my sub levels. If the PS3 could bitstream, I'd be a happy camper.
The lack of analog outs is a non-issue for me and the lack of an IR receiver is unfortunate, but the workaround isn't too much to bear. I don't think heat or noise will be significant enough that I'll ever notice (I'm used to running a 360).
Anyone want to talk me out of it before I take the plunge?
It's not a true home theater unless you have a projector. Oh, and popcorn.