I don't like 'em at all.

The theory behind why they're "ergonomic" is that they allow you to rotate your elbows outwards, which is supposedly a more natural position for your forearms on the keyboard, and supposedly avoids some repetitive motion inflammation in your wrists. I've never seen this to be the case. Every time I've been forced to use one of these keyboards, I end up taking it off the desk, pulling up a more conventional keyboard and plugging it in. And I'm a touch typist who can still do 70+ WPM on a good keyboard on a good day.

For my money, I judge keyboards by how their keystrokes feel first and foremost, then I worry about the keyboard layout.

IMO, and most people won't agree with me, much of the carpal tunnel and repetitive stress from keyboards could be relieved if we ditched the QWERTY layout and went to Dvorak layouts.