Replacing XBMC
The PS3 is getting fairly close to XBMC these days. It talks quite happily to my MythTV back end over UPnP and it'll already play back all the recordings and music that it indexes. Granted, most of my stored video is Xvid, so it won't do that yet, but the codec is coming in a firmware update quite soon. XBMC still has a considerable edge on file type support and navigation, but the gap's narrowing - and the PS3 can play back full HD content. I've got a dedicated front end HTPC as well, but it's usefulness has been eroded somewhat by Sony's recent firmware improvements.
On games, the Xbox360 undeniably has a better range for now, but the exclusive titles for next year don't make brilliant reading for the Microsoft evangelists. The PS3 may yet come good - the previous generation consoles shifted something like 125M units over their lifespan (and the PS2 is still selling well) - no vendor has got much of a share of the likely final install base just yet.
The Wii is a lovely device, very well thought out - but I think it is likely to have expanded the overall size of the console market as much as taken sales away from the more traditional units. Most of the "serious" gamers I know with a Wii have got at least one other console as well.