I can play copied games, I can load games straight off the hard drive, once I buy one, I can load game saves to and fro the computer and the ps2, I could install linux on it if I wanted. pretty much anything you want to do with one you can (including changing the id of the unit)
but the biggest thing is the copied games thing
a friend of mine has over 80 games for his x-box.. imagine getting that for free.
im just getting into it myself, so I don't yet know of all the uses yet myself, but of coarse I like the act of hacking it better than reaping the rewards of hacking it.
in short the most common things you'd want to do with it are
play copied ps2 games from dvd or from the hard drive
play copied ps1 games ...
play emulated games (SNES, SEGA GENESIS, SEGA MS, ATARI ect. ect.)
play divx movies, xvid, vcd, anything else in that category
play mp3's, view jpg's ect.
play copied dvd's (without taking a risk of ruining the laser)
memory card emulation with pen drives (something I've definetly got to setup)
codebreaker software (for those of you that like to cheat, to each their own)
that covers the gist of it, the basic stuff that you'd do.
93 mustang notch
~450hp 331 stroker - Sold