Rated 4 out of 5 stars
I installed this on Firefox 8 and it just works. I'm using a dark user style, so the math PNG images were atrocious (and the native Wikipedia MathML rendering doesn't seem to work at all). This add-on finally solved the issue for me, thank you very much.
One thing I don't like is the big button in the status bar (useless on most pages anyway), but I just collapsed it with some JS and call WikiMathConverter.Convert().