[Brian]

These weren't actually removed - Apple's added additional system-wide uses for those gestures in Lion. They override the app-specific uses.

If you re-map the system-wide gestures, you should be able to use them in OmniWeb again. (I don't have a trackpad on this machine, or I'd walk you through the process.)

A google search on "browser tab swipe lion" turns up a number of similar questions from folks since Lion shipped... If you find a link with steps that work for you, please post it here for other folks in the future. Thanks!