I have the A4tech 8-button mouse, mainly because it was on sale. I don't have any real use for 8 buttons, but it's nice to have a couple extra apart from the usual two and the buttons doesn't get in the way either.

It's a very good mouse, i had a Logitech cordless optical but it drained batteries like nothing else!! It got a little bit better when i started using a lighter mousepad, with the black pad i had originally the batteries lasted two days at the most! With the lightgrey pad they last four or maybe five days.
Not good.

The A4tech is with a cord but it doesn't bother me, i'm not about to take the mouse out for a walk...