It's funny that this topic should come up now... this weekend I have the projector from work home.
While full-wall gaming is indeed pretty ridiculously awesome, you need a really dark room or else everything looks really washed out and dark colors are difficult to see. Even in a completely dark room, the projector I have here (a Dell 2300MP, a quick glance online says it's ~$1200) still doesn't look that good when it comes to the dark colors, and I've tweaked all of the settings as much as possible.
That being said, anything with bright, vibrant colors looks alright. Playing Sonic the Hedgehog on a 2 meter wide screen is pretty fucking awesome.