My journey for the perfect keyboard has lead me on this route (in the order I used them):
1) MacAlly Ice keyboard- ok keys but broke way too easily
2) Kinesis Advantage Pro- Seemed like a good idea but I came to the conclusion that having your hands completely locked in one position is not good for my RSI. Keys (brown cherries) were nice, maybe a bit too light even for me, and using the thumb for so many modifiers was giving my thumb pains.
3) Unicomp buckling springs- keys waaay too hard.
4) Das II- Decent all around... I like the keys (blue cherries) but it's two-step action is little weird. I like it enough that I haven't returned it but can't quite see using it permanently
5) HHKB Pro II- I like the keys the best so far-- very smooth action, keys are light enough. My only wish is that it had more modifier keys (ie, it could use a control key on the right side, as well as full size Alt keys.) and arrow keys. Not very good for windows development because visual studio needs arrow keys/function keys.
Given this, what should be my next keyboard? Ideally, there is a keyboard out there with keys at least as light as the HHKB, arrow/home/pgup/down keys, function keys, no num pad, full size control and alt on both sides.