How fast is fast?
Chrome's "canary" build -- the least stable and most advanced version of the browser -- was 40.5% faster than the "dev" edition and 43.5% faster than the current "stable" version.
SunSpider scores showed that the canary edition was just 2.2% faster than the dev build and only 3.5% faster than the stable version of Chrome.
The reason for the discrepancy? Sunspider's tests are many small tests where Chrome doesn't have a chance to show its mettle. The real tests will start when Crankshaft starts hitting mainstream Chrome builds in the next month or so.