I don't think it looks uncomfortable to hold, as I only hold a mouse with the tips of my fingers anyway, but does it have a middle click, eg mouse wheel click? If not I don't want it. And does it have side buttons? Not required, but a nice feature.
I agree, middle button and side button functions seem to be missing, which will be a serious problem.
I stopped at the Apple store today to try it out. Sure enough, no middle or side buttons, so no quick way to access widgets or Expose. Nothing in preferences to fix it either. I asked the sales guy and he didn't know, but went to ask a tech. The sales guy said the tech says there are a lot more mouse button options in the preferences coming in 10.6.2, but he (sales guy) didn't know yet if there were options for addressing the middle and side button issues. Seems like there ought to be some way to use the multi-touch to fix that, but I'll believe it when I see it. Definitely this mouse is not acceptable for use with the currently available mouse button preferences.
The scrolling did seem to work well, but they weren't very imaginative with the multi touch capability. For instance, you still have to hold the control key on the keyboard to zoom with the mouse. I would have thought they would use the pinch / squeeze zooming tricks of the iphone and stuff like that. I would have thought it would be able to operate in a touch pad mode for controlling the pointer too. Scrolling was not a noticeable improvement over the scroll ball on the current Mighty Mouse.
It seemed very uncomfortable to hold. It's possible that I'm just too tall to comfortably hold a mouse at the low counter height at the local Apple store, but whatever the reason my wrist was hurting badly within just a few seconds.
We'll see what happens in 10.6.2, but without some significant upgrades this could be a very bad mouse. I'd like a chance to try it in a friendlier setting too, but if the wrist pain issue is not a function of the store set up, this could very well be the worst mouse Apple has ever made. Too bad, it's an innovative concept that may well be critically flawed in execution.