Not the guy you replied to, but I switched to Colemak last year. It took me about 3 weeks to get to a "usable" state, and maybe 2 months to get within 75% of my previous speed with qwerty. My progression was roughly:
0-1 weeks: Can't type anything without looking at the key map. I would switch back to Qwerty if I needed to type something long out (emails mainly).
1-2 weeks: Weird phase. I can't effectively type in either qwerty or Colemak unless I really "focus" on it. It's hard to describe, but this week was terrible for productivity :)
3+ weeks: Forced myself to use Colemak exclusively. During this time I started doing real typing exercises, and turned off autocomplete in my IDE, since I found that was detrimental to learning. I also wrote a ton of documentation for a couple of my projects, which involved a lot of typing.
Before I switched, I would get intermittent pain in my wrist (maybe twice a month), which has since completely disappeared. When I need to type in Qwerty now, it is very uncomfortable, in a way that Colemak never was.