Shake Hands with the Zero Tension Mouse

That looks pretty slick. Looks easy on the hand.

 

It looks good. It takes care of the most important elements: supporting and rotating the wrist so weight is not put on the inside of the wrist (where the carpal tunnel is).
By doing these two things it also brings the wrist into a natural angle (not bent on two axis and twisted).
The only thing I don't like is that you need to almost make a fist to use it.
This is not a natural hand position and can lead to claw hand (like a regular mouse can). It is still a big improvement over a regular mouse.
The larger size is needed for the wrist support. Unless you are really short on desk space, this is not a big deal. A larger mouse pad (about the size of a sheet of paper 8 1/2" x 11") would be a good idea.