I believe it is only the old 60gb models which are backwards compatible, and they are like gold dust.
I am a BIG fan of the PS3, but mainly because of what it can do other than games… eg:
Games
Watch films on Blue Ray, DVD, and over the network from my PC
Watch TV with PlayTV – and port it to my psp at work
surf the net
Will prob end up getting an Xbox 360 too though as I dont really know what else to do with my money 🙂