Super excellent.

It's brilliant. $5 for well-supported application with free upgrades. Opera's gestures have spoiled me and only xGestures can match it :)

New version came out recently, and it's fully supported in Leopard. This app is great, and is definitely worth the 5 bucks. Once you start using gestures, you'll wonder how you ever got along without them.

xGestures is an excellent and essential utility. Mouse gestures greatly enhance your control over your applications / OS. Brian Kendall has done an amazing job at creating a powerful yet elegant inteface to manage your application and global gesture settings. Global gestures can control iTunes / system volume / manage running apps and more.

You can exclude gesture support for specific apps (e.g. Opera or Firefox which have their own systems).

You can visualise entered gestures, and allow the gesture mouse movements to also pass through to the app or not.

You can also specifically target dialogs / sheets.

It is the best $5 I've spent in a long while :-)

Since I became a Mac user I've bought a number of shareware programs. At just $5 xGestures is the cheapest and yet it's still the most useful. I would be prepared to pay $30 or more for this because I use it every minute of every day.
Once you've set up some basic gestures, this program will completely change the way you work. When using another system I often find myself instinctively gesturing and wondering why nothing is happening. And it's that instinctive integration that makes xGestures so amazing - it's so seamless I don't even realize I'm using it.
Sure, it takes a little while to set up and memorize your gestures (I recommend putting a help sheet next to your monitor for a few days) - but once you start using xGestures, you'll find it difficult to stop!

This is potentially my favorite utility ever! I can't use a machine without it. Awesome idea, and an incredible workflow improvement.