I got one and couldn't get used to the grip at first since I have small hands.
Then I changed it up so that my middle finger always sits on the scroller.
I've found this style of playing to be very effective for fps gaming. But it sucks when you're in Windows. As a result, I use my cheapo Logitech First Mouse for everything other than first person games.
Like the others said, see if you can try it before you buy it. Or do what I did, take a plunge, and get used to it