While Archibald did these tests on OS X, the results are interesting enough to share with Phoronix readers. The test includes an animated background, transform, and border radius on 499 elements. His results?
Chrome Canary - 15 FPSDamn! Servo is delivering some serious performance. The test appears to be done with Servo's new GPU-accelerated rendering backend.
Mozilla Firefox Developer - 9 FPS
Apple WebKit Nightly - 5 FPS
Mozilla Servo - 60 FPS