I bought a Wacom Pen and Touch Small, and here is my report.
First of all, the power cord is way too short, but luckily my work's help desk hooked me up with an extender. My first impression was a solid design, and a relief that I hadn't purchased anything bigger. This thing is the same size that you would expect from a stand alone touch pad mouse, but maybe slightly wider. Anything else would have just increased fatigue. I love that the pen has two buttons and the pad has four. That gives me plenty of places to map, and already makes the set up more efficient than a mouse (keep in mind my selection of mice is limited, I can't buy a mouse with twenty buttons).
The pen takes some getting used to. Using your fingers to touch works exactly like any other touchpad, with similar mapping as a Macbook. It's great for quick adjustments while I'm coding. When I'm really using the GUI, however, I pick up the pen and it's great. It takes some getting used to, about a full day of programming plus a few hours of Rome 2 (playing strategy games with a pen is excellent). Once I mad the adjustment, it really is faster and more comfortable than a mouse. I still dislike using GUI's in general, but the Pen is so natural for a person to use.
As an aside, the driver's on Windows are supposed to download automatically, after all, Wacom wrote and tested them. I had to go to the website and get the driver, and install in manually. I switched to Ubuntu, praying that the drivers would be an easy install, and wouldn't you know if the kernel already had some open source drivers ready to go for me. Ain't Linux great?
The Wacom is, of course, a blast to use with Gimp, photoshop, blender, etc. I definitely give the thing my recommendation if you're looking for an alternative to a mouse, although I obviously cannot speak to whether the use of a pen or touchpad will save your wrists. Only time will tell.
To give another wacky alternative to a mouse, I also own a leap motion plus. I keep it on the side of my desk, and when I'm on a web page I use my finger to go back and scroll up and down. I definitely don't recommend switching a mouse out for one, they have terrible accuracy for on screen clicking and pointing, but mapping general hand movements to one can allow you to go literally hands frees. What's more ergonomic than that?