There hundreds of games on pc steam and theres like 1 on the ps3, the point of ps3 steam is the cloud. Cross comparability is for valve games only
Its not even cross compatability. If you buy a PS3 copy of portal 2 you got a code for the PC version. You can't play cross platform PS3 and PC/mac. Only ps3/ps3 and pc/mac. I do believe that you can chat with friends on steam cross platform though.
You can't play cross platform PS3 and PC/mac. Only ps3/ps3 and pc/mac