RoboHornet is a new Browser performance benchmark that aims to test real world performance of modern web apps.
To summarize the initial results (it's still in Alpha) Chrome dominates on all platforms except Windows 8, where IE 10 handily defeats it.
The result I found most interesting actually, was how poorly Firefox fairs. In all of the other synthetic benchmarks, Firefox is quite competitive, indeed even beating Chrome on Mozilla's own Kraken benchmark. But on RoboHornet it's not even close. Firefox loses to everyone by wide margins.