You can aways adjust the screen mode... i prefer an 4:3 mode.
A few SNES games runs too slow (Top Gear and DKC3) but Megaman and others series is full playable at top speed. The sound save state issue was been resolved in Rukas´s SNES_TYL...
Anyway Genesis emulations is not perfect... some games crashes or doesn´t work well in DGEN 1.70 . PSPgenesis 0.18 runs the games wich doesnt work in DGEN but some games runs slower. I have both in my MS.
NES, Master System and older consoles emulation is perfect.
The most problematic emulation which i found is the PC-Engine one... HUE and PCEP are not perfect and each one have diferent problems... but you still can have a lot of fun with then.