Up to the release of Firefox 4, my browser of choice’s add-on compatibility record was awful. The surest way to break an add-on was to update the browser to a higher version number. Since Mozilla have moved to an accelerated release schedule, they issued a call to devs regarding the compatibility issue, and it appears their efforts are meeting with success.
I’m running version 7.0a2 (the Aurora channel), and all 14 of my add-ons work. All but one are officially compatible, and that one functions perfectly. See for yourself:
In other news, there really is NO reason whatsoever to be running the release version of Firefox. Switch to the Aurora channel: it’s just as stable – if not more so – than release, has much better performance and unlike Chrome’s Dev channel features aren’t routinely broken overnight.