Of course You can play BF3 online on 42" LCD while seating on a couch with KB+M. I do it on a regular basis
CIV5 or Shogun - why not? Works for me at least. De gustibus...
Anyway - kudos to Valve for bringing it, it won't hurt anyone, it's just like an optional skin for Windows Media Player. They should make it switchable at will.
For me it looks like just another step before showing us the Holy Grail - "STEAMBOX".
HL3 a STEAMBOX exclusive?