I bought the mighty mouse for one reason: scroll wheel.
It really does make my life easier, but while still using the one button form that I'm used to. Like Blue Velvet, I mostly use keyboard commands which makes things flow a lot quicker -- it also REALLY impresses people and makes you look like a total robot.
I programmed my mighty mouse to use the scroll button to trigger Expose, which works wonderfully. I never liked pushing a key to activate it, so this is much easier and has streamlined my operation quite a bit.
But the mighty mouse does need a lot of work before it's perfect. If you go in the Peripherals section of the forums, you can read about all the problems I had with it.
Fishes,
narco