It's ran all the games i've thrown at it so far. Most homebrew apps didn't run though, or ran with problems, that I expected.
So far I've run these perfectly fine on my JTAG unit:
Fusion Frenzy NTSC
Halo 2 NTSC
Halo 1 NTSC
Halo 2 Killtrocity Modded Map discs (1 and 2)
Burnout 3: Takedown NTSC
The Simpson's Road Rage NTSC
Rallisport Challenge 2 NTSC
Jet Set Radio Future NTSC
Sega GT 2002 NTSC
Crimson Skies NTSC
Star Wars: Knights of the Old Republic NTSC
Latest T3CH XBMC Build, Quake3, and Windows ce.net (lol) did not load, or caused a hardlock, that's the only homebrew i've tried so far.