I tried a few games, here's what I got, I'm using the MOD 1 version, loading the games from my thumbdrive (all those using the classic controller using the Dynarec core):
Castlevania SOTN: Works flawlessly, got a bit of slowdown and the sound got a bit choppy on larger areas, but I turned the dithering option off and it got pratically perfect, really need to play this one again
Castlevania Chronicles: Background music is weird, apart from that it's totally playable
Intelligent Qube: Perfect
Strider 2: Perfect
Marvel Vs Capcom: Restarts constantly
Strider: Restarts constantly
Mortal Kombat Trilogy: Restarts constantly
Capcom vs SNK Pro: The 2nd controller is acting all weird, making it impossible to play Arcade Mode. I managed to enter the Vs Mode and realized the game would be perfect if not for that problem
Guilty Gear: The same problem regarding the 2nd controller, the game seems to run a it slow, though.
Mickey's Wild Adventure: Works perfectly, no background music, though (it might be CDDA)
R-Type Delta: Works, but slow
Darkstalkers 3: Works, the music is glitchy but it's totally playable
Both Street Fighter Collection 2 and Street Fighter Alpha 2 didn't worked
This emulator surprised me, I didn't expected to be that great, too bad most of the fighting games are not working, but mostly are due to small bugs, if those bugs get fixed someday, it'll be almost perfect.
Now I need to get a few more games to try it out, and dig out my GC controller to see if something changes..