For its upcoming Firefox 4.0 release, Mozilla has been concentrating a great deal on what is often cited as the main shortcoming of Firefox ... its speed. For example, Firefox 4.0 will include GPU acceleration for both rendering and compositing on Windows 7/Vista, OSX and Linux, and it will have GPU acceleration for compositing only for Windows XP.
Given their charter and ostensible mission of helping people, Mozilla have been tracking the performance of their Jaegermonkey engine aginst the equivalent engines within Safari and Chrome using the sunspider and v8bench benchmarks (as opposed to their own Kraken benchmark) for some time now. In this way people cannot accuse their results of favouring Firefox.
Enjoy it when it becomes available soon for the first time in Firefox 4.0 beta 7.