I converted to the Notebook Optical Mouse as a desktop mouse about eighteen months ago, and haven't looked back. I find that using a heavier mouse is now actively challenging for me - I find the larger type sluggish and unresponsive.
The added battery weight of the Notebook Wireless Optical is enough to put me off - that's how light this little sucker is. As a result, I own five of them. One for home, two for work, two for the laptop (and just as well, as my girlfriend's mum's bird - a cockatiel - gradually chewed through the USB cable while on holiday a year ago, while warming itself near the laptop fan). I'm a big fan. I recommend them heartily.
The scroll wheel on the home mouse has been getting a bit non-scrolly recently - you can scroll down all you want, but sometimes scrolling up just stuck, and it would take a couple of attempts.
After coming up blank with searches like "disassemble notebook optical mouse" and "open notebook optical mouse" and "break open mouse", etc, I resigned myself to buying another one, then pulled out the tool kit.
Cutting a short story long, remembering there are no user serviceable parts, if you do decide to void your warranty (I guess; didn't bother looking) by opening one, here's how to avoid my mildly-finish-damaging mistakes in opening it:
Once you understand that, everything else becomes easy. A lot easier than breaking the red side panels off with a screwdriver while looking for the magic unlock clips. Hmm.
The screw is under the large black skid pad at the bottom of the mouse. The last place I looked - I did actually check the front feet, and the hologram logo as they looked like the most likely screw-hiders. Peel the black thing off with something sharp (mine re-stuck with no problem), and once the screw is removed, you can lift the top from the Microsoft logo bit - there are a couple of clip/hinge/catch things, one each side of the mouse cable. Once the screw is gone, it's easy.