Just tried QuickNES. The first thing that confused me was the SMDH info - it just appears as 'Retroarch 3DS' on the Homebrew Loader. When I actually loaded it though, it seemed to work okay until I tried to play Super Mario Bros. with it. Then I just got a blue screen.
After that I tried loading Megaman 3, and it ran for like three seconds, incredibly stretched to the point where only 25% of the screen was visible, before crashing the entire console as soon as I opened the Retroarch menu.
I restarted the console, tried again, and got the same problem, except this time I didn't open the menu. The game loaded the titlescreen, I pressed start, and the console crashed when reaching the Robot Master Selection screen. So there's that, I guess.
Judging from the sound, though, the emulation seems to be near-full speed, if not full. So I have high hopes in this emulator.