They are awesome! They really improve the user experience making it so simple to pull up the multitasking bar and for getting back to the home screen. I hope they can somehow implement this for the iPhone with less fingers needed.
If you have a Mac, I think this is a must have add-on. Just download for free Xcode version 3, plug in your iPad and once it's recognized, click on "use for development" and then disconnect and you will have the new gestures in your General Settings section.