Mozilla Accelerates Firefox 5 Release Schedule
conceivablytech.com
conceivablytech.com
The total development time for a version is 18 weeks, but there will be several versions worked on in parallel. In other words, when one version is in beta, another is in experimental and so forth.
So in theory a release is possible every 6 weeks. However, a decision might be made to not release (depending on open bugs) and wait for the next window, which would make it 12 weeks.
I'm still moving along happily with 3.6.17 until the extension developers get all their kinks out and someone invents a more perfect/compatible statusbar replacement.
FF4 has tons of improvements, I'm incredibly glad I updated despite a bit of a rough transition.
There is also http://support.mozilla.com/en-US/questions/791489 and some other web pages reporting this problem.
Looks like for most people the problem is that FF4 is now using direct2d DirectWrite for font rendering where available, and DirectWrite has some issues.