We did a little run-down of the Steam PS3 functionality in the wee hours of the morning, but our chums over at Press X or Die have had a proper look, complete with images.
The whole thing actually looks pretty functional. I was expecting something with many creases to iron out, but it seems Valve have gone with the simplest routes for navigation and displayed information. Achievements, Friends, and News are all there, as is a full functioning chat. You might want to invest in a little bluetooth keyboard though, as PXOD’s image puts it “Typing with a dual shock sucks balls.”