The long development of Firefox has left many a crashed browser in its wake. But a recent study undertaken by the Mozilla Metrics team shows that the relatively new Firefox 3.6 is much more stable than Firefox 3.5. As each release matures, the rate of crashes goes down with each update. Version 3.6 has already surpassed 3.5 in overall stability, having gotten about 40% more stable since release.
Another interesting statistic uncovered by the study was that Firefox 3.5 started out significantly less stable than version 3.0. Firefox product lead Mike Beltzner explained that the cause was 3rd party applications. The 3.0 build was what took Firefox into the mainstream and developers began building on top of it in larger numbers. When the code was altered in version 3.5, many API calls that worked fine before caused crashes.
Whatever the cause, we're certainly happy to see Firefox improving over time. Now that we've got these numbers, you've got another reason to update if you're still on 3.5.