Firefox v1.5 was released some time ago, but I only just got around to upgrading a few days ago. I had read such great things about the new release, I was anxious to try out some of the new features. It was quite a shock when the application proceeded to crash 8+ times in the 2 days it took me to getting around to troubleshoot the problem.
A tip: If you have Adblock installed and plan on upgrading from Firefox 1.0.x, UNINSTALL it before (or soon after, trust me) upgrading to the new version. Adblock Plus is the compatible extension for v1.5. Unlike my other extensions, which were automatically disabled if an update couldn't be found Adblock seemed to be working normally (ie ads were still blocked), but it obviously caused stability issues.