Yeah, I've had no issues with anything I've emulated. There is a plugin you can use called Powertools that you can use to limit the cores the Deck uses to improve fps stability. Just youtube it.
Old games I tested:
Gamecube - SSX games, Gauntlet Dark Legacy, Eternal Darkness
PS2 - Chulip, NFL 2k5, Shadow Hearts
Dreamcast - Crazy Taxi, Dynamite Cop, CvS2