I will say after using any one of the Logitech mice that have the ultra-smooth roller bearing scroll wheel (a number of their models do), there's no going back. That in combination with the forward/back buttons makes web browsing so much easier and quicker.
As a right-hander, I have gotten so used to the Performance Mouse MX (formerly MX Revolution) shape, that when I pick up a regular shape mouse, it feels wrong.
Steve