This year for Christmas I bought myself the Natural Ergonomic Keyboard 4000, and I have to say after about a month of use, this is one very nice keyboard. Before I got this keyboard I was using the standard Apple keyboard which caused my wrists to hurt after about 30min of typing. This keyboard doesn’t bother my wrists at all, the split design along with the elevated center really does relieve stress on my wrists. The programmable keys at the top are also very nice- and they are fully functional on OS X! What surprised me most was that it only took me about a week to get my typing speed up to what it was before and after about three weeks of use, my typing speed is considerable faster than before with less typing errors.
My only gripe about this keyboard is the ‘zoom slider’; this would be much better suited as a ‘scroll slider’. I scroll alot more than I zoom.
I would highly recommend picking one of these up, I was able to get it for ~$45 at Amazon; but it looks at though they changed the price.