Comment 263 for bug 125970

For what it's worth, under my setup (see comment 150) the above site uses 40%, then 20% of the total processing power on my machine during scrolling (it changes about 1/4 of the way down) and has a very noticeable back-and-forth visual jerk at the bottom.

I realize completely that such a live site without a reduced test case (which we already have) isn't very useful. But, it's an interesting real-life example of how this issue and others can collide to yield exceptionally poor performance.