One big caveat with these results: they are all run on my MacBook 2GHz CoreDuo with 2Gb RAM running 10.5.1, and the Windows benchmarks are run under Windows XP in Parallels 3. Having said that, I've had similar results to those that others have posted for "real" windows installs, and they should at least be relatively significant. Also, the Windows benchmarks had quite high error percentages, so YMMV quite a lot. Anyway, enough waffle, here's a pretty graph: What's most impressive here is that Safari on Windows is seriously fast - over 20x faster than IE7! Weirdly, it's also over twice as fast as Mac WebKit despite the fact that it's running inside Parallels! There's no Mac Opera because 9.24 crashes on launch for me, and their 9.25 download page currently 404s. I've attached the spreadsheet of results as a PDF in case anyone's interested. Updated: I added Webkit Win and Opera 9.5b win, and I retested IE7 to see if it could get any better, and it improved a bit - now it's only 15x slower. Updated: I had a go at running Mac Opera 9.5b, however, it fails to run all the benchmarks, or at least fails to report the timings correctly (the tests themselves appear to run ok), so doesn't come up with a final score. The offending result is:

regexp:                  NaNms +/- NaN%
    dna:                   NaNms +/- NaN%

Updated: I spotted the Opera 9.5b Mac benchmark values manually and dropped them in - results are not amazing. Also added IE6 on Win2k (also in Parallels) which got very good certainty values of ~1.5% but hysterically bad results overall! Updated March 18th: Added Safari 3.1 and updated the Mac WebKit results for today. Added FF3b4 - a big improvement over 2. Added IE8 - a welcome showing for MS now they have seen the light. I removed IE 6 and 7 as their performance was so bad that it was making the graph hard to read!