In a recent Firefox 3.0 status meeting it was revealed that there are 700 bug classified as 'blockers' or bugs worthy of delaying release. Given the original timetable for the project, it seems that things are running slower than expected and it is a good guess that the delays are due in part to the number of show-stopping bugs.
“Firefox 3.0 is months behind the schedule Mozilla set about midyear, when it said the browser would reach Beta 1 in late July and move into a second beta in September, both preceding a final release by the end of the year. Now, however, the company's Web site alludes to getting Beta 2 ready by the December holidays.”
Participating developers have until Thursday to prioritize their bug-lists so that the bug-squashing can begin. We're eagerly awaiting the final product, but the general consensus of most forum users on the forums we patrol is that they'd prefer longer product betas if the alternative is buggy releases.