Just picked one up. I would have to say the multi touch is great. It is probably the best mouse I have used. I have large hands but the ergos don't bug me one bit.
The only small complaints I have are:
- the multi touch gestures are not the same as the track pad on the macbook (generally they are one finger less). This isn't a big deal but it does take a bit of time to get used to
- the tracking needs to be faster. I have a 24" ACD and with the 15" MBP I have to pick up the mouse and "reset" it to track all the way from one side to the other while keeping the mouse on the mouse pad.
I would like them to fix the second "problem" which can be done with a software update. I have already got used to the first issue. It is actually easier to use one finger less with the mouse, however, it did feel unnatural at first.