That looks well designed and very easy to use, I just wish someone designed similar products shaped for the left hand - these are all but useless to me for anything more than short term use (entirely my choice and strong preference).
edit: the MS optical intellimouse is the best I have found so far for features and lefty friendly design, the good options are limited from what I have seen so far.
edit2: did a fresh google search and
this came up at least.