I've only tried SNES, and only briefly. I think the controls are alright... probably better for games where you don't have to be super accurate or fast. Couldn't imagine playing, say, Mortal Kombat on it. I'm a big fan of old SNES RPGs, so I was playing a little Chrono Trigger. Controls are fine, actually better than I expected. The sound, however, is a bit choppy and tends to actually slow down (which drops the tone, as well. It's almost like someone slowing down a recording). This sucks, especially for games like Final Fantasy III(US) and Chrono Trigger, which have my favorite video game music.
I haven't really had the chance to go through all the settings and whatnot, so it might be able to function better with a little finagling.. who knows?
Hope this helps!
I should get NESoid, I bet it runs smoother seeing how the games are smaller