Ok after a bit more time with thecontrols, the only caveat I have is that the joystick is not ideal as a trackball replacement for games like Centipede.. and I think this could be improved with a patch for the app.
Still, I had a blast playing it last night. Especially enjoyed Major Havoc, Asteroids, and Tempest.
TIP: Many games default to landscape view (i.e. Tempest), but if you want to keep the iPad in portrait orientation, there will be a setting for that in the game's options. If there isn't a "landscape/portrait" setting, change "Controls" to "Arcade".