Sony supports it - http://www.playstation.com/ps3-openplatform/manual.html
"Computer" wise its not amazingly fast or anything - but its not slow at all either.
The ability to play xvid/divx is sweet, and of course everyone will be porting all the Linux Emulators over to the PS3 soon enough (i believe SNES and Genesis are already running - not perfectly of course yet, but running)....
Theres no 3d support yet - so no linux games/wine games. Again im sure soon enough some uber linux dude will get a driver for that too...
Software/Programs? Firefox, Thunderbird, GAIM, IRC, FTP, etc etc. VNC too. All the little bullshit desktop games - solataire, minesweeper, etc. Office suite, programming suite, libraries, all that stuff too.
Personally im sure I wont use it much more than watching TVrips on my TV, but its pretty cool nonetheless... Plus who knows in the future maybe they get drivers for like camcorders, digi cams, etc plug em right into your PS3... Or maybe like USB TV Tuner - BAM - now you have a HTPC/PS3. External BluRay burner one day? who knows - but if enough of the Linux community starts rocking it - there will no doubt be a shitfuck of programs/drivers ported over