I switched to dvorak a few years ago and to thumb-key this year. I would say that thumb-key is much easier to learn than dvorak. I simply switched to it and about three months later, I realized I had gotten up to almost my original typing speed without any directed effort. I originally typed at 45 wpm on AnySoftKeyboard, and now I type at 40 wpm on thumb-key. This is in contrast to dvorak, which took six months of at least 15mins a day of dedicated practice time to surpass my original speed.
Did you continue to use Qwerty for work? I was in the fortunate position of switching to Colemak at a fairly non-critical time of life, so I cold turkeyed it.
Took about two weeks of daily driving until it was no longer painful, then three months until I had matched Qwerty speed. So probably similar to your thumb-key experience.
Faster than Dvorak. Unlike switching from fluent QWERTY to an initially slow other-layout, you're switching from the frustrating autocorrupt to something deterministic and predictable.
I picked it up to a usable speed within two days, helped by the fact that I use a lot of technical terms that autocorrect used to dismantle, so the baseline was much worse.