I use them extensively, since we often use them on our machines (due to lack of space for a mouse), so I've had ample time to become adjusted. Heck, I've even used them (and mice) with gloves on, in cleanrooms for long periods of time. (Typing with gloves on is interesting)

I'll still take a mouse over anything else for a general purpose cursor mover -- and I've used multiple versions of just about everything (mice, trackballs, pointer sticks, touchpads, graphics tablets, touchscreens, cursor keys).

It still comes down to personal preference -- and trackballs don't work the best for me.

Tony