Just started today.
I've been touch typing qwerty very fast for ~9 years, and the switch is really hard... despite being called "easy". :)
But I can already feel that it'll be worth it. The fingers "jump around" much less. It feels awkward to have such an easy access to everything. :)
My motivations to switch are to reduce the risk of ever getting RSI, and to become more efficient of course.
This is a great layout. I only recently heard about it. Before, I only knew about Dvorak, which would be a bad choice for me.
But colemak preserves almost all the special characters, and zxcv, which is just wonderful. (they have good positions on qwerty)
I still have to look at the layout picture all the time though, and I'm incredibly slow... this post took me ~30 minutes. :(
But I'm not giving up. This is a very smart and promising layout. I'm not going back anymore. :)
I have the layout pic (Colemak_fingers.png from this site) set to "Always on top" and am now writing on colemak in IM, forums and the shell (Linux), always looking at it. I think that's a good way to learn it.
Common mistakes so far: confusing i and L, e and i, r and s. I'm also particularly slow with the upper row, pgjl in particular.