BTT is great, even if you just use it for little things. You have all kinds of options for a bunch of complicated gestures if you want, but I mostly just like it for the ability to change the function of existing gestures. For example, I took out the app switching from 4-finger left-right, right-left and made it call up in-app expose (which is especially useful for going between your main Mail window and a message you're composing). I also use a 4-finger click to call up the Dashboard. I just wish I had something useful to do with the three-finger click.