Okay, I finally tried it. I really thought that the Mouse Gestures thing (all-in-one Gestures) was gonna drive me nutz. The idea is that you can control many of the functions of your browser with some mouse gestures.
What is a gesture? You hold down the right mouse button (on windows) and draw on the screen. So, if I want to open a new tab; I hold down the right mouse button and draw a line "Up". This opens a new, blank, tab for me to use. To Close that tab I right click, draw a line Right, then down, then left.
It sounds more awkward than it is. I tend to be a keyboard guy; I learn the shortcuts and I try not to use the mouse. There are some things (like web surfing) where that doesn't work as well (try tabbing through an RSS feed or a Digg Screen *shudders*). Gestures make it much easier.
Once you get it installed, you need to learn one gesture: Down-Right-Down
This gesture opens up a window with all your gestures so you can see what you can do without having to open up the AddOn Options for All-in-one. You can then tweak what you like to use. I geeked a bit here; I took the screen and photoshopped it into a quick reference card that I have next to my monitor. I also turned off a lot of the extra ones (I don't need zoom-in/out etc.) so the sheet is pretty small.