First, I want to heap praises and gratitude on DreyMar for the Tarmak progression and all the others who have contributed here. It's great!
I came to Colemak by way of randomness. I discovered alternative keyboard layouts when I started googling "best keyboard" to find a good, ergonomic mechanical keyboard. A few clicks later, I'm finding out the QWERTY layout is a bad hangover that won't go away because the world is lazy. How exciting! I had to try it for no other reason than it's better and faster than the old way.
1. What layout you've been using beforehand, and how long you've been typing with it.
I've been a QWERTY user for 15 years since learning to touch type in grade school. Granted, my touch typing was never incredibly solid despite all the Mavis Beacon games I played. Probably broached an average typing speed of 60-70wpm.
2. How long you've been using Colemak for, and how many estimated hours per week you've typed with it.
I've been typing vanilla Colemak for about four months now. I type 40hrs/week for my day job and write at home quite a bit, 7-10hrs/week at a minimum.
3. Mention the methods you used to learn the layout.
I decided to learn Colemak through Tarmak due to the benefits of gradual progression with minimalized loss of productivity. I needed to maintain a reasonable typing speed for my day job. Tarmak was perfect for this. I spent about four weeks on each level to maintain productivity at work. This was a surreptitious switch that my boss certainly didn't know about. Probably would not have viewed it in the best light, but they never found out, so hah.
4. What operating system you're using.
I use Mac at work and Windows at home.
5. Typing speed.
I'd switch to another level shortly after I regained a 30-40wpm typing speed. My job is particularly suited for this because it involves repetitive typing of common single words. Conversely, it has made broaching >50wpm a much slower crawl because of the limited vocabulary involved. So, I hovered at 50-55wpm for a few months on full Colemak with very slow progress in speed. Currently, I finally tested at 61wpm on http://patorjk.com/typing-speed-test/.
6. Share any tips about learning the layout.
The only difficult level was the final one before full Colemak. I actually spent a couple of months typing in this one because it was a much more difficult switch. Most likely because I'd decided to only spend one week on the level before it, so my mind was still committing that map to memory while also applying the new keys. I confused L and P pretty often for awhile. Tarmak worked really well for my situation. I had to be able to type quickly at work, so it was an easy choice. A couple keys at a time was just fine. Tips? It can be a bit of an annoyance to a SO if you share a computer and they're not exactly computer savvy. There were some frustrated growls when gibberish appeared instead of the expected keys. Plus a "Why are you doing this?" moment that was a bit exasperating. Too bad! Ctrl+Shft or Shft+Shft is quickly learnt!
I also get delightfully incredulous looks when keyboard layouts come up in casual conversation. Not that they do, really, but it's a nice, obscure conversation topic, that's for sure.
Edits for format & additional info.