I have the 120 gig slim now, after my 60 gig one packed up, and other than a larger hard drive; I’m pretty sure they’re the same hardware…
Personally I don’t think it is as reliable as the fat version, I’ve had far too many times where this slim has failed to power off, resulting in me having to pull the cable out the back, it’s hard locked a couple of times also; but that could just be the game.
I’d still recommend it though, if you already have a 360, a PS3 is just as much as a must-have, if only for the exclusives.