I love Apple products, but I'm sorry, if you have to use it for work 8 hours a day it is not a good product. Of course there are exceptions and some people (on this post) will love it, but for most people this is a badly designed tool. It's too bad, because it is a great innovation. I got one with a 27" Mac at work and despite it's great functionality, it is the worst mouse I have ever used solely because it is so ergonomically incorrect and uncomfortable to use. Sadly this thing reminds me of the hockey puck mouse from the first iMacs. I love the way it works, but it feels like it was designed for aliens. A mouse is simply a tool and should feel good in your hand. This is like the best hammer ever, but the handle is a pencil.
The Good
The vertical scrolling and momentum on web pages and applications (like the Outlook inbox in a VM) is phenomenal and performs better than one would expect. It is fast, smooth, and responsive, yet is still precise. The scroll functionality is way better than a scroll wheel on a typical mouse, no grinding noise and much better. This particular feature is a great innovation. It's like using your iPhone to control your app windows.
The Bad
To use it you essentially have to place your hand flat or grasp it with the tips of your fingers to move it around. I have hand pain just using it after a few days. If you think the Mighty Mouse is uncomfortable and feels bad to your hand, wait until you try this thing. My hands are pretty average or slightly more than, so I am physically a mainstream user.
It is wireless only, so you also have to worry about another battery in your life.
More
If they would just make it much more rounded so it actually felt comfortable for the palm of my hand it WOULD be a wonderful device. Perhaps they can't do that and have the touch scroll which is why it is so flat. The "journalists" who gave this thing glowing reviews when it first came out have no excuse, it is immediately apparent when using this thing that it is a poorly designed device from the ergonomic perspective which supersedes the otherwise great functionality. Several other employees here have had the same reaction to it and I have yet to see anyone like this after the first 10 minutes. Replacing it with a cheap HP USB mouse felt like a Godsend.
Too bad.