I've got one much like that one (and have had similar in the past) and no matter what I do, I find the extra side buttons are too far forward to be of any use without moving my hand from a comfortable position: if the left buttons are under my thumb, my middle fingertip is so far forward, it can't use the scrollwheel without contortion, and my left and right mouse button fingers are perilously close to touching the mouse mat. My hands aren't huge, but they're not tiny, so I've never been able to work out who has a hand with a thumb the same length as their fingers (maybe they're designed for oranhutans?).