Those are very general conclusions to draw from one test case. The bouncing ball test runs at 60 FPS for me on macOS; most of the time is spent in painting, as

Those are very general conclusions to draw from one test case. The bouncing ball test runs at 60 FPS for me on macOS; most of the time is spent in painting, as expected. Likewise, Stripe scrolls at 60 FPS for me. I should note that the bouncing ball test is the kind of thing that WebRender is designed to improve—painting-intensive animations—so it's obviously untrue that there's no interest in improving this sort of workload. When running your bouncing ball test in Servo with master WebRender, I observed CPU usage of no higher than 15% (as well as 60 FPS)…