User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:9.0a1) Gecko/20110925 Firefox/9.0a1 Build ID: 20110925030856 Steps to reproduce: Scrolling, especially when using a trackpad, such as a Magic Trackpad, is not smooth, especially on longer, complex web pages such as engadget or facebook. Actual results: Scrolling appears choppy and sluggish. Expected results: Scrolling should be smooth, even on more complex web pages. Perhaps render the entire page and pan along the rendered image rather than rerendering a web page as it scrolls?

WFM on: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:10.0a1) Gecko/20111103 Firefox/10.0a1 and also on Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0) Gecko/20100101 Firefox/8.0 beta 6 I'm using for testing a Magic Mouse and the scrolling is made smoothly. I have used for testing www.engadget.com

This is still true as of the November 13th build. For comparison, Chrome on the same machine, displaying the same content, scrolls very smoothly.

In particular, scrolling is not smooth when elements of the page are still downloading. Chrome is smooth regardless of whether elements are downloading. But some pages, such as engadget, continue to serve content for several seconds. Firefox is not smooth while the download is taking place.

Actually, trying it on news.google.com, it's not smooth on Firefox even after a completed download. On Chrome, it's always smooth.

Could you try with addons disabled? However there are many bugs like this for slow scrolling (and slow smooth scrolling) on several pages.

Tracking this in bug 675866.