It's been a while since I've posted anything about my wrists. I've mostly had them manageable, although my left wrist still hurts quite a lot much of the time. But based on a couple of people asking me specifically for what I've been doing for my wrists (hoping it would help them as well), here's some quick, non-professional, I-am-not-a-doctor-or-ergonomoist things I've found that help:
First, exercise with negative resistance is very helpful. Negative resistance is where you're working against a force (such as walking down a steep hill). The best device I've found for negative resistance on the arms is the Powerball gyroscopic exerciser; I got mine (which I'm very happy with) from NSD Powerballs, but there are a bunch of other ones on Amazon that I haven't tried. They're a bit hard to learn how to use at first but it's worth the effort.
Another important thing is to take typing breaks and to stretch during them.
These days I use RSIGuard, which costs $65 (and has a 45-day trial). On Windows and Linux there's Workrave which is nearly as good (although it doesn't track actual usage/strain and its stretches aren't nearly as comprehensive or well-designed). The least-terrible free RSI timer I've seen for MacOS is TimeOut, although it's pretty bad (which is why I eventually broke down and bought RSIGuard). During these typing breaks is a pretty good time to use the Powerball.
July 2012 I no longer recommend RSIGuard on the Mac, as it's fragile due to some underlying design flaws (which mostly come down to its Windows and corporate-deployment legacy). Unfortunately there are some issues with Mac OS X which makes it difficult to make a properly-working typing break application (because of some strict "user-friendliness" issues when typing break software must be inherently unfriendly), but the application I use which is the least bad, all things considered, is BreakZ.
A good ergonomic setup is also very important. Most keyboards are way wider than they need to be (pushing the mouse further away than is really comfortable), and most keyboard trays suck badly.
I use Apple's wireless keyboard and trackpad (which also work with Windows with a bit of effort, and also in Linux) and instead of a keyboard tray I use Ikea's DAVE laptop desk, which is nicely height-adjustable, easy to place in a comfortable spot, and pretty much stays wherever you put it. It's way better than any of the $300 professional keyboard trays I've used.
July 2012 I've been using a Filco Tenkeyless keyboard (a clicky one at work and a quieter one at home). It's only somewhat better than the Apple Wireless Keyboard, but every little improvement makes a big difference. The price is pretty off-putting, though. As far as a pointing device I've gone back to a normal scroll mouse, although I think that's been detrimental. I still haven't found a perfect pointing device.
Finally, when I sleep, I usually wear a wrist brace. I like ACE's TekZone ones; they're much more comfortable than any of the others I've tried, and are easy to adjust to be tight without being constricting. They're available on amazon although I'd recommend going to Walgreens or CVS or whatever so that you can size them properly.
Of course, I'm not a doctor or an ergonomist or whatever, so if you have access to a professional ergonomist definitely take advantage of it.