Very honestly, it boggles my mind just to try to imagine how one can accurately control a mouse with that thing. It feels so much like an analog joystick, and as such, it doesn't have a way to enter an absolute motion.
Trackballs, touchpads, mice, even a lot of esoteric solutions such as eye-trackers do. Even Valve made a controller with touchpads to work around this problem.
I find them too slow for long distances too, and they tend not to be accurate enough if you increase the speed.
I had a couple of friends at university looking forward to have some of those, but they admitted (on their own, while presented with the above argumentation) it was for the "premium/professional" look of those rather than usability.
So,in my highly subjective experience, this input method is highly unusable when used as a mouse. I wonder how you perceive these issues? Maybe I am just using them the wrong way?
Edit: One thing I wish more laptops had is a third button, though, if only for interacting with tabs/link in the browser, and copy/paste.
You can also use a touch pad with your thumb quite accurately (tap to click), but it's a bit awkward.