How I began: https://forum.colemak.com/viewtopic.php?id=1111
After little less than 10 months of using Colemak, I can now consistently type at 100+ WPM according to the tests I've taken online.
So after using it for 10 months, I can confidently say that switching was a great idea for the following reasons.
I type faster than I did with Qwerty, and it will even get better over time as it has only been less than a year.
It is less stressful for my hands/fingers.
In addition, typing on Colemak feels like it takes much less effort. My hands don't really need to move around.
My friends always get confused when they try to use my computer. It's quite funny to see them keep hitting backspace for several seconds until realizing something is not right.
There have been difficulties, but not anything major (at least once I learned how to deal with them).
One difficulty was gaming that uses Qwerty. For quick games (like flash games online) that needs Qwerty keyboard, I can easily change layout with either a hotkey combination or clicking on the Language Bar. For other games that I play often, I just need to go to settings and change keys. Something like Starcraft where hotkeys are not only positional but also depend on the letter is more tricky, but in this case using Grid Layout solved the problem.
Another difficulty was using other computers. If I just need to type a few things, I just look at the keybaord and use my two index fingers. Otherwise, I set up this url so that I can download an executable Qwerty-to-Colemak program: http://qnfauf.com/qtc.exe. (Feel free to use this anywhere. I made this using autohotkey. Use Shift+Space to toggle between Qwerty and Colemak.) It only takes a few seconds to download and run this on any computer, and I am good to go with Colemak.
Using Korean with Colemak was probably the most difficult thing for me, but this probably does not apply to most people. I could easily set it up so that I can switch between Microsoft's Korean IME and Colemak, but the problem was that the Korean IME is based on Qwerty. It means that if I were to use hotkeys while Korean IME is being used, it will be Qwerty. After an extensive research, I found an IME made by a group of people in Korea that support Dvorak and Colemak. It is a bit buggy, but I am happy with it. I just hope I can continue using it in the future because it is not being managed by anyone. If that happens maybe I will just learn how to make IMEs :) (If anyone here is Korean, 새나루 is the name of the program.)
So if anyone is wondering if switching to Colemak is worth it, I would say go for it if you type a lot. It really is better than Qwerty. Most people will not have to worry about another language not working well with Colemak, and non-gamers do not need to worry about games.