I've been learning for 2 weeks and 2 days, and I've just I switched to stage 3 of Tarmak. I'm coming from 20+ years of QWERTY, I've got over 100 wpm on typeracer in the past.
I tried Colemak years ago; I got to R and S in the Colemak lessons I was following, got too frustrated, and gave up. Before, learning Colemak was a slog. Now it's a game. I got to level 3 today!
Edit: here's some more about my situation for anybody reading this trying to assess what commitment it might be for them.
I'm sure you can approach direct-to-Colemak in the same way, but approaches that way don't give you the reward of letting you type real text fluently every few days, with a nicer layout every time.
So I think I've learned two things since then:
1. 30 minutes a day is plenty to make rapid progress and in fact is very efficient -- no need to knock myself out with longer than that per day or force myself to do real work with it until I'm quite familiar with the layout already.
2. Incremental reward is important. Everybody knows that, but I think it's hard to take sufficiently seriously. I think that leads people to concentrate on the problem Tarmak introduces of relearning key sequences, and not about the reward Tarmak provides of being able to type real text fluently every few days, with a better layout each time, both of which are not to be sneezed at. Learning Colemak in one step before, I *was* getting the "incremental" part by restricting myself to a few keys at a time, but not the same "reward" part as being able to type any text I feel like, nor of regularly getting a new better layout.
I think there's a survivorship bias in the Colemak community. If you're here and you're not learning still, that's because you were sufficiently highly motivated or skilled to make it to the end. People who were not are by and large not here posting, and I expect there are many more of those than there are here. If those people had more incremental reward, I suspect more would make it to the end. In fact the 30 minutes/day thing is more of the same, I think: it makes progress fairly painless and incremental.
Of course there *is* another barrier there that Tarmak adds (apart from re-learning key sequences -- bigrams etc.), which is getting the Tarmak layouts working. The reason I found that part easy was just that I was already very familiar with flashing my keyboard's firmware, because I started using an ergodox. Of course there are software routes, but they're a bit of a pain, I find: room for improvement there (I wonder if debian/ubuntu are open to contributions to package them up...).
Anyway, of course I still have a long way to go and have not really conquered even R and S yet (but E and G etc. are solid), so it's a bit soon to be proclaiming my success and great wisdom ;-)