I've been using the deskmount Evolution keyboard from Ergo Interfaces on my main work machine for a couple of months now. I've been doing so both because of some chronic wrist pain, and to try actually using the split-keyboard approach to things. What follows are my own personal tribulations and truimphs using said technology.
The keyboard itself, as seen in this older photo, is split and angled, with the touch pad in the upper-left corner of the right-hand section. As you can see from the image, it's a full size keyboard -- complete with numkey area, real function keys, and all that.
The primary difference between the version I tested and this older one is that rather then being mounted on arms of the user's chair, a la the older Evolution, the new keyboard sits on the desk.
There's a whole steel/metal mounting system that you have to install on the underside of your desk. Luckily enough, I use the TJ series desk from Herman Miller, which came with the appropriate mounting system already installed. Otherwise, it'd be a remove-everything-from-desk, flip-over (because the mounting system is heavy) and careful-work ordeal. You need to hold the mount perfectly still while you drill in the eight screws that hold it in place.
However, since I already had a keyboard/mouse mounting tray installed, the tray for the new keyboard fit right in place -- no fuss, no muss. I suspect that it's a standard size, so if you have an average-looking mounting system in place, you may be able to just use that.
Again, the only big difference between this and the other Evolution keyboard is that it's made for the desktop, rather than chair mount. Doesn't sound like much, does it? Believe me, it is. One my big complaints with the chairmounted Evolution was that you couldn't roll your chair over to another part of the room, because of the length of the cables hooked to the computer. And moving the arms of your chair loosened the screws holding the keyboard in place. Over the six months or so of Rob using it, the screws slowly stripped till they could barely hold the keyboard up. The desk mount with this version makes a big difference in this department -- far less hassle.
My other big complaint about the keyboard, though, hasn't gone away: the mouse sucks. It's a small touchpad surface, and the mouse buttons are horribly non-responsive. It's also a two-button mouse, so you have to chord for the 3rd button, and having non-responsive buttons means that cutting and paste becomes a difficult process, under any *nix. And because the pad is so small, you really have to turn up the sensitivity to be able to move around at 1024 x 768. There was software included with it, but for Win9X only, so that didn't really help out much.
So, the mouse is frustrating. The desk-mount fix is good, but I'm switching back to a more regular setup, until the mouse situation gets better. But if you have do wrist problems, or want to take an ergonomic approach before they appear, this keyboard is well suited for that. And if you are running mostly Windows, then the mouse issues become less of any issue -- no need for the 3rd mouse button, and the software on the disks will mean better support.