Steps to reproduce:
0. Requires a Mac with OSX 10.7 Lion for smooth trackpad scrolling (via laptop trackpad or external mouse/trackpad)
1. Download project from github (https://github.com/njx/mousewheel-test) or see attached zip
2. Open mousewheel-test.html
3. Follow instructions to perform a medium to large scroll
4. Observe output graph
The graph shows wheelDeltaY values for the duration of the "mousewheel". The attached sample graph shows large anomalies during acceleration and jittering towards the end of deceleration.
Created attachment 131718 [details]
Graph of mousewheel event wheelDeltaY on a MacBook Air running 10.7.3 Lion
Created attachment 131720 [details]
Archive of test project from https://github.com/njx/mousewheel-test
Are you seeing this with Safari 5.1.3?
Yes. Tested with Safari 5.1.4, Chrome 17.0.963.79 and Webkit nightly r110587.