The tests were performed using a fully up-to-date Windows Vista SP2 installation and the Windows 7 release candidate on the same machine. The results show that when looking at stable releases, all browsers show a performance boost when run on Windows 7 as compared to running on Windows Vista SP2, with Safari 3 leading the pack with an 18% speed increase, and Opera 9.64 coming in last with only a 2% speed increase.
Moving on to the latest non-nightly test builds, the picture is completely different. It seems that everyone except Apple is testing their next browser release on Windows 7, since Safari 4 beta 528.17 saw a dramatic performance drop of 22%, while all other browsers' test releases saw speed improvements between 12 and 16%. Chrome 184.108.40.206 and Firefox 3.5 beta 4 led the pack here, both coming in at 16%.
The results neatly summarised in a chart:
The tests on Safari 4 were run multiple times just to confirm them, but the results were the same every time. Still, it probably indicates a bug somewhere in Safari 4, which will probably get fixed soon enough. Overall though, these figures indicate that browser users - which means all of us - will enjoy a faster browsing experience on Windows 7.