I've been thinking about getting one of these keyboards, a Microsoft Natural 4000. It's a pretty slick design with decent key feel, although a little chunky. Plus it's got lots of buttons, and it's hard for me to pass up a gadget with lots of buttons.
I've used ergo keyboards in the past and liked them a lot, but one of the things that's always bothered me about them is that the 6 and B keys are placed on the left side (for the left index finger to hit). My problem is that when I learned to touch type, I use my right index finger for those keys so my typing tends to come to a jarring halt when I go for those keys and hit nothing but air. Well, nothing a little bit of retraining won't take care of. Touch typing habits die hard though.