Ten days after the first Firefox 4 release candidate the second one (RC2) was released. According to Mozilla milestones this is the last release candidate before the final release of Firefox 4 that will take place on Tuesday, March 22, 2011.
So what’s new in RC2? According to Mozilla Wiki “Two very small, very isolated fixes in order to better protect Firefox 4 users.”
I have switched to FF4 RC1 several days ago (and upgraded to RC2 today), so the final release won’t be that of a change for me. If you haven’t upgraded yet, start making sure that all add-ons you use are compatible with FF4 and working.