V8 doesn't optimize the code when it first compiles it to machine code. There is a second compiler that is much faster so V8 has to pick and choose which functions to send through for better optimization. The old V8 would stop every millisecond to look at the current functions to see which ones were worthy of optimization. It was great for longer functions, but the smaller functions would finish before ever being optimized.
As previously said, the new V8 engine is now available in the beta and dev channel releases of Chrome. That means that it's still under testing, so be sure to download the latest release to test it out before it hits the stable channel release.