This touches my nerd bone in a nice way, even though I hate Flash. Props.
That being said, this neither runs at full speed nor supports audio. The SPC700 audio chip is notoriously expensive/difficult to emulate, often being more of a challenge than the rest of the console. (Native code has been able to do it accurately for well over a decade though, which should give you some idea of how well Flash's VM performs..)
I remember the old days when they first added the SPC700 support. I believe it necessitated figuring out dynamic frameskipping which is something we see in almost every emulator today (and has been put to good use on low powered hardware like my GP2x Wiz).
ZSnes was my goto for a very long time since it just ran faster on my hardware. But Snes9x is really the SNES reference software.
Actually, SNES9x and ZSNES are both pretty buggy, and include hacks to make individual games run correctly. Allegedly ZSNES 2.0 is under development with improved accuracy, but who knows if or when it'll ever be released.
The true SNES reference software is bsnes, with no per-game hacks and only three known-incompatible games (and then only because they use obscure co-processors that nobody can find any references for):
http://byuu.org/bsnes/
Be warned, though - bsnes is a sub-cycle-accurate emulator of a reasonably-powerful hardware platform, and so has surprisingly steep hardware requirements (any desktop processors released in the past couple of years should be fine, but people who still haven't upgraded their Pentium 4s are likely to be in for a bit of a shock).
I wish I could upvote you twice. This is a great find. I've long assumed that Snes9x and ZSNES were the top of the pack w/r to SNES emulation. I'll have to check this out.
That being said, this neither runs at full speed nor supports audio. The SPC700 audio chip is notoriously expensive/difficult to emulate, often being more of a challenge than the rest of the console. (Native code has been able to do it accurately for well over a decade though, which should give you some idea of how well Flash's VM performs..)