Hey,
I've been using Colemak for probably more than two years now (can't remember how long ago I didn't).
Things that are awesome:
1. Caps Lock -> Delete : saves so much time once it is second nature to fix errors this way (which it is for me)
2. Z, X, and C unmoved for easy cut/copy/paste
3. Easily type special keys like áãéíó by holding down alt and ctrl.
If I have any complaints, it is that I can definitely feel the increased right-hand stress over the left; maybe that doesn't mean anything ergonomically but I find it a tad annoying.
No doubt Colemak pwns qwerty and dvorak though (I tried both). Can't say anything about the other layouts.