It depends what you will be using it for.
My advice would be to get a different mouse (possibly a tablet instead) if you ever do photoshop work. It's no good for any CAD programs either. I use both of these a lot, and have found the Might Mouse useless for these tasks.
However, for web browsing, e-mail, word etc... It's a fine mouse and is a godo buy if you're willing to spend a bit more for something that look's geat next to your Macbook. I've heard that the wireless version is quite heavy, although this is not from my own experience.