The Finger Track Ball Mouse is quite unique out of all the computer mouses I've used. Whats different about it is I use my thumb to move around the cursor on the screen with a ball in the mouse that resembles a marble. Clicking to go to places on the mouse is like pressing a trigger with the finger closest to my thumb. You can just hold the mouse in your hand without moving it on a flat surface. My thumb basicly does the most work when operating the mouse. The mouse may be awkward and takes some getting use to, but I personally adapted to it quickly and really like the mouse since it required very little effort to use when compared to other mouses I have tried.
As far as wrist comfort the USB Finger Track Ball is the most comfortable I've ever used. Its so comfortable I could use it all day without any discomfort.
This is one drawback about the mouse when it comes to using an average mouse that you would use for a flat surface. If I adjust the cursor speed just right(which is the most difficult thing in my situation)i would prefer to use the trackball mouse more than any other mouse. Adjusting the cursor speed for accuracy took time and experimentation for me to be satisfied. I will further say adjusting the cursor speed in order to suit my needs took more time than nescessary but I blame it moreon my computer not adjusting the cursor speed slow enough to get it at its most accurate.
Also its important to keep your hands clean as not washing your hands after eatting a greasy meal and then using the mouse can effect the traction when using the ball to move the cursor.
As Long as you be careful and don't accidently drop too much it should work fine. I've found this mouse if accidently dropped too many times to be among the least durable. If you drop it too many times like I did over time the ball that moves the screen cursor will come out and basicly is exactly like a marble. You can put the ball back in the mouse and secure it and it will work, but this will cause it not to move the cursor as well over time while also making it harder to press the trigger to go to links while surfing the web. Common sense says take care of it, lol enough said.