Wow: great idea. I think, technically, the picture's a little blurry (which is strange, as your shutter speed was clearly fast enough to totally freeze the guy in mid-air), but the matter of the photograph more than makes up for it.
Nice sense of action; whole picture seems slightly to lack focus and compositionally would like to see more of the audience rather than having them blocked by the figures
Street performers are always fun and part of city life, wish you had been standing at another angle though, looking at everyone's back is not that much fun..
Interesting - I'm not totally sure what's happening though. Perhaps a big back-flip or something. The inclusion of the audience is a nice touch. Perhaps more focus on the performer and less on the distant audience would work well though.