I just got my hands on the new Apple's Magic mouse, featuring a multitouch surface with gestures support.
Sleekness is apparent:
Canon 40D, Canon EF85mm 1.8 USM, 1/200s, f/1.8, ISO 160
So far it's behaving good and I'm not feeling it being slow, like some people have mentioned. People with bigger hands might feel that it doesn't have the proper ergonomics, but it fits in my palms very smoothly. It takes some time, though, to get used to it's low height.
I was expecting that because it's actually a trackpad on "wheels", the clicking is gone, and that you just tap to click. Well, I was wrong. The clicking is still here, loud and crisp, just that the whole surface moves down to click, sort of like on the new unibody MacBooks.
Scrolling provides a really good experience, and it's performed with just one finger moving on the surface. It works like on the multitouch trackpads, where you can seamlessly scroll in any direction (including diagonally).
I'm thinking of getting one mainly because it works over Bluetooth, so I'm left with one unused USB port. The fact that it looks awesome doesn't hurt either.

Gesture support currently falls a little short, as currently only back/forward navigation is supported via two-finger swipes. It would be useful, to at least offer all of the gestures supported on trackpad. I'm missing the pinch-zoom the most.
Luckily this issue is easily fixed via a software upgrade, so no worries there also.
Canon EOS DIGITAL REBEL XTi, Canon EF85mm 1.8 USM, 1/250s, f/1.8, ISO 320