Mighty Mouse R0x0rs
At the risk of being pegged an Apple apologist, I must say I'm really enjoying my latest purchase, a Mighty Mouse. It replaced a cheapish Kensington unit with two buttons and a scroll wheel, so no, I'm not just now discovering the joys of multiple mouse buttons.
The scroll ball is fantastic. Not so much the horizontal scrolling (which, let's face it, doesn't come up all that often), but the feel of the thing. The squeeze buttons are kind of a pain: I have to shift my normal mouse grip to use them, so I've assigned them to the Dashboard that I only use a couple of times a day anyway. The right click, despite the apparent lack of separate buttons, works perfectly (at least the way I right click: I never noticed this before, but I always lift my index finger up when right clicking. Maybe one of those unconscious things like how I raise my pinky when I'm drinking from a glass. Er, nevermind).
Anyway, if you have a Mac, and extra $50 burning a hole in your pocket, and you're on the fence about the Mighty Mouse, I'd say go ahead and take the plunge.