VGS doesn't work within Classic, unfortunately.
It's almost perfect, but some games (Rollaway) don't render properly. Certain games that used special tricks (i.e. addressing specific registers on the video processor directly) are a bit glitchy.
PCSX has a problem with CDs that have audio tracks. On Leopard, you can just eject the audio part of the CD and the game will play, but you can't do that in Tiger. I've found that it doesn't work at all in Linux.