The perception that Firefox is a slow, but very customizable browser could convince a lot of users to try out other browsers, as speed seems to be one of the main metrics in picking a new web browser.
Recent Sunspider and V8 Benchmark tests run by Rob Sayre suggest that Firefox made a huge leap performance wise. In Sunspider, the latest Firefox 4 with Jaegermonkey enabled managed to complete the test in almost half the time it takes Firefox 3.6.9 to complete. But even with those improvements, Firefox 4 finishes fourth when compared to Opera, Internet Explorer 9 and Google Chrome. The gap however has been closed.
In Google's V8 benchmark, the performance increase is even more visible. The performance almost quadrupled compared to Firefox 3.6.9. Firefox 4 with Jaegermonkey enabled showed a better performance than Microsoft's Internet Explorer 9, and managed to close in on Webkit. Both Chrome and Opera on the other hand are far ahead in this benchmark.
The developers have promised that more improvements are being implemented in the coming months, which suggests that Firefox may perform even better in those benchmarks than it does at the moment. The good news is, Firefox 4 will be a lot faster than Firefox 3.Advertisement
Already using the beta 5 and and waiting for the improvements