Well, I guess I have to say Das Keyboard now. I've never used it (like most other people, I suspect) and so won't comment on how useful it is or isn't.
I know they claim that they've changed the springs on some of the keys depending on what finger you typically use to push those keys, but that's assuming that you type correctly (home row and all that). If you're not a good touch typist and/or you're looking to improve your speed, I guess it's not the worst keyboard you could use.
For technogeek factor, I would certainly suggest it, but for a good keyboard...? I use the Logitech Elite Keyboard (without drivers installed) and it works fine for me.