Magic Mouse: Touchy in a good way.

The hardware:

The Apple Magic Mouse sports a touch glassy surface with an aluminum underside. (From the pic left-to-right) The underside contains a green LED light to indicate operation with a slide switch to toggle on/off, the laser/reader hole and a latch to access the AA batteries.

For battery life, since it has only been a week plus old with me, the battery is still going at 93%. However, if you do some reading online, you can form your own opinion on the battery life since there are tons conflicting reports on it so it is best you make your own judgment. For myself, I switch the mouse everyday once I power off the system and the mouse do go into power saving mode on idle, so far so good!
(Note: The original packing of the mouse comes with a set of original battery inside, so original battery life may not be a best gauge as it depends on how long the mouse has been sitting inside the warehouse before shipping to you. This is from the local Singapore online Apple store original battery life may differs in your country)

Usage
Mouse usage is the same as other typical mouse. The mouse uses bluetooth which shouldn't be a problem for Mac users as all Mac ranges comes with integrated Bluetooth as standard.
The only two main different point:
1) The touch surface usage.
2) The comfort level.

The Touch Surface
The mouse comes with an integrated button under the touch surface, so although you don't see the physcial cut-out of a button, you can still feel the "click" when you depress the mouse. In face, nearly all the mouse surface is clickable this means you can even click on the mouse using your palm, if you want to. Right-click option is configurable under Mac.

The touch surface starts above the Apple logo and goes all the way up, so a generous portion of the surface allows tactile touch contact using fingers. I won't go through the mouse operation as well as multi-touch operations (using multiple finger gestures), this is well documented on the web, such as this video by watchtechnews:  Magic Mouse Gestures

Magic Mouse supports finger gestures

For first-time to Mac users, it may be a bit weird getting use to the touch functions. However, the movements are quite intutive as it is modelled after the typical mouse with scroll wheels. Only the new functions such as finger gestures will need some time to remember and use.
For Macbook users, it will be natural if you have plenty of experience on the Touch pad on the Macbook range.
For Mac users, it will be short learning curve if you have been using the Mighty mouse or normal mouse, your learning curve is expected to be shorter due to the familiarity with the Mac OS platform  compared to first-time Mac users.

The Comfort Level.
The Magic Mouse does not score well in this, as mentioned above, most of the mouse surface are Touch enabled. This, in my opinion, may be the reason why the Apple engineering team to adopted a flatten surface instead of the curved surface that better gripped the palm.

Flatten Surface For Touch Contact

Typical Mouse with a curved body

Due to this flatten surface, finger gestures are enhanced, on the expense on comfort. Thus the mouse may not be suitable for: Gamers, Designers (CAD/Adobe CS/etc), etc where the bulk of the time is spend on gripping the mouse for productivity. But the mouse is excellent for users such as multimedia consumption (surfing the web, simple office productivity, etc) as well as a good choice for Mobile users/Road warriors due to the wireless option.

All-in-all, the mouse integrates a cool design, with looks as well as multiple Touch capabilities gives new air into a decades old device and making users think on how a mouse should function as well. However, if you belong to the die-hard group where you must feel tactile contact of a scroll wheel, see the mouse button, the mouse contours must blend into your palm then it is best you should give this a mouse a miss because it has none of the above.

(Magic Mouse works on Windows via boot camp on a Mac. However, again, if you using on a non Mac machine running Windows, it is a risk, although drivers are available, it is not official from Apple. There might be a chance during future updates, the mouse may become inoperable on non-Mac Windows machine so I take no responsibility if you are planning to buy it for your Windows machine)