Thanks to Blur Busters bug reporting efforts (Issue 310848 + Issue 320955), Google Chrome is the new champion of smooth scrolling at 120Hz.

It now beats Internet Explorer 10+ smooth scrolling. To get perfect 120Hz or 144Hz smooth scrolling (via arrow keys, and via middle-click autoscroll), you must use Chrome 33.0.1723 or newer (and Aero enabled), available as the Chrome Canary pre-beta. If you don’t want early betas, wait for the public Chrome 33 release in early 2014.

Blur Busters continues to help web browser improvements, see 120Hz Browser Tests.