In short: Awesome.
Good things: Being able to put keys anywhere is just wonderful. It's like going from ints to floats for keyboard layouts.
I have used the layout visible in the first picture to play Anno 1404 yesterday and it was great.
I also absolutely love the open source driver. It's easy to install and easy to use and just generally wonderful. Programming a key takes seconds.
The obvious downside is that it doesn't even have mechanical keys. Somebody said something about rubber domes but to be precise they're buckling rubber sleeve. Still suck, of course. The sticky pads that are used to keep the keys on the plate don't work very well either but I'm assuming that's because I've got a used one. Some of them stuck to the plate instead of the key when I tried to move it.

The keycaps are also not particularly pretty. The have stickers on them, the legends are not centered on the stickers and the stickers are not centered on the caps and no the effects don't cancel each other out perfectly. :p
All-in-all I can understand the fuss this caused when it came out. It is easily the best thing to use for gaming when you have one hand on the mouse and one hand on the keyboard.
The way you can move the keys, reprogram them and even use macros makes it incredibly useful and because it works so simply and smoothly it makes you use it without hesitation.
At least that's my opinion right now. I will try to find some time to test it with Starcraft. That should give a pretty good indication.