http://www.w3schools.com/browsers/browsers_stats.asp

Mozilla accounts for 9%. Better than nothing, I guess, and at least it's growing steadily, but I don't know how much of a dent it's really making. Big sites though, yeah, I notice that Amazon and CNN and sites like that are pretty much guaranteed to work in Mozilla-ish browsers.

EDIT: I consider stopping midis from playing to be a handy feature. I don't know how to fix it; it might be possible, but I wouldn't want to if it was.