We're still in beta, and it will probably improve quite a lot in the upcoming months, but I use it myself on a daily basis.
For the record, the emulators are currently based on Emscripten versions of the libretro cores (rather than being a full-JS emulator implementation, like IodineGBA). I'm looking to add more consoles, and the SNES will probably be come soon.
Should you try it, I'd love to hear your feedbacks (my contact is on my HN profile) :)