I'd just like to clarify something about the mighty mouse... about the right click.
You don't have to do anything special on the RIGHT side of the mouse (somebody said you had to reach to the top of the mouse).
The problem is, you can't be touching the left side of the mouse at ALL. Shortly after buying my Rev A intel iMac I discovered that the mighty mouse will register EVERY click as a left click if there is any contact on the left side of the mouse. In other words, you must lift up your left finger when you click with your right finger.
I went back to the store and explained this to an employee there, and he confirmed what I was afraid of: that this was simply how the mighty mouse works, and there really isn't any way around it : \
I've gotten used to it, and I love the scroll ball for most things, however, I will admit that it's still not my choice of gaming mouse.
Another issue is that you can't right click and left click at the same time because of the reasons I listed above... as long as you're left clicking, u can't right click... at all. That makes it a no-no for games like Halo where you want to toss a grenade in the middle of shooting.
Also, the scroll ball, though, like I said, great for most work, doesn't do great with games. Many shooters allow you to scroll through weapons or perform other actions by moving your scroll wheel one click at a time. Problem is, the scroll ball is so sensitive that it's nearly impossible to move it only one click forward or backwards. I also accidentally brush against it sometimes.
Lastly, the squeeze buttons on the side aren't great. I'd much rather have two separate buttons that I can click. You can't use them independently (you have to click both at the same time), and it's too awkward an action to be able to do it quickly in a game.
I've been using a cheap Kensington Optical Elite mouse in a box. It's nothing special... just your standard left/right clicks with a scroll wheel (which is also a button, of course), and one extra button on each side of the mouse.
The mighty mouse is a great concept, but it's just not very practical for games : \