I have read a lot about the new Firefox 3.7 and Firefox 4.0 that should increase the speed and compensate for all the new features and CSS3 and HTML5 support that the competition has developed. By competition I mean mostly Google Chrome, Opera and partly Safari. Mozilla roadmap says that we can expect Firefox 4.0 beta release in the end of June 2010.
I have downloaded the latest nightly build of Firefox 3.7 preview from Mozilla FTP. The release I have downloaded was Firefox 3.7 alpha 6 preview dated June 12, 2010 (firefox-3.7a6pre.en-US.win32.zip). I have unzipped it to a new folder and gave it a test.
I have repeated the tests on the same (blank) profile in the older version of the browser and the results were still very similar. So it looks like that the new Firefox 3.7 will be 1.4 times faster than Firefx 3.6.