Since I'm in denial about having carpal tunnel syndrome, I'm always trying new ways to make it go away. One form of treatment I have found that works pretty well is to switch out my mouse about every 30 days. I have a pretty decent collection. I have been anxiously awaiting the release of the Natural Wireless Laser Mouse 6000. Microsoft's web site has said "coming soon" for months. Last week I decided to search some online vendors to see if they knew when it would be released. Buy.com actually had them in stock. I bought two with overnight shipping.
This is not your ordinary mouse, but it is so much more comfortable. It does take a little bit of time to become comfortable with the new shape. Once you do, you will not want to use anything else. It has all the features of the new mice: scroll, zoom, etc. All I can say is that is much more comfortable and causes less wrist strain, but it could still be improved.
They really should make mice in different sizes. The Natural Wireless mouse could be slightly larger. It's not much larger than some of the compact mice. Microsoft could also take a few notes from Logitech on wireless hardware. I also just purchased a Logitech MX Revolution. The MX Revolution has a very small USB stick for the wireless receiver. Microsoft is still using those "bricks" that are larger than most mice. The MX Revolution is also rechargeable, whereas the Natural Wireless takes two "AA" batteries. Personally, I prefer the disposable batteries instead of rechargeable. When the batteries are dead you can just pop in replacements. Instead of waiting for a recharge, which I had to do twice on the MX Revolution.