"IETester is a free WebBrowser that allows you to have the rendering and javascript engines of IE9 preview, IE8, IE7 IE 6 and IE5.5 on Windows 7, Vista and XP, as well as the installed IE in the same process. "
I've benchmarked Google Chrome 9.0.597.10 and 10.0.603.3 (with Crankshaft) and the latter is 30% faster. See the detailed results: http://dromaeo.com/?id=124912,124913