I'm still rocking one of those right now. Early 2008 version if i'm not mistaken. Will only run snow leopard. Also, I've gone through two batteries. The one I'm currently on has warped so bad that I can't use it since it presses against the bottom side of the keypad and trackpad, and I can't accurately use either. I have to have my laptop plugged in and hope that I don't accidentally knock off the magsafe connector and lose what I'm working on.
Also, it gets dirty very quickly for some reason and the plastic has become very brittle around the edges.
Clearly, a rMB will be a big step up for me.
EDIT: NM.... I don't have the unibody one... it probably would have been a step up from my 2007 white macbook since I wouldn't have the plastic chipping off where the keyboard plastic meets the bottom case. In any case, I think I got my money's worth since i've had it for 7 years now.