Seems like the default gestures for navigation are now using 2 fingers, since 3 fingers are used for mission control etc. But the problem is, pretty much nothing supports this. The only thing I see that supports it is Safari. What happens if you need to navigate back in Finder, or iPhoto, or any other app? You can't! Seems like a usability conundrum. I thought Apple would figure this out, but it's DP4 already and everything's the same. I've set up Lion now to use 3-finger navigation and 4 fingers for Mission control etc. This works. I wonder if this will end up being the default, though I'm sure Apple wants as few fingers as possible. Any thoughts on this and how they can fix it?