Just decided to try my hand at Colemak today (~4 hours in). I've happily been a Dvorak user for about 5.5 years now, but I have a good chunk of free time now. When I was learning Dvorak, though, I made sure I remained proficient at QWERTY as well. I have about the same typing speed for both, but Dvorak is just much less fatiguing (also, my vim muscle memory only associates with dvorak). Talking to friends who have learned it, however, they seem to have completely switched, causing their QWERTY familiarity to go down the drain.
So, my question for the GH community is, when and if you've learned a new layout, did you maintain your proficiency for the original? If so, are any of you proficient at 3 or more layouts?
As for my experiences with Colemak so far, I've noticed the following:
* Compared to Dvorak, it took less time to memorize the layout
* Due to its similarities with both QWERTY and Dvorak, I make many more mistakes when trying to type using muscle memory (relative to when I was learning Dvorak). For example, when I only practice the home row, I often get the keys confused with Dvorak's homerow, but when I practice the home row + the top row, the confusion lessens. A similar phenomenon happened when I was learning Dvorak originally and sentences/words would start with A's or M's.
* I find that I dislike the placement of H, J, K, and L.