I used the Colemak layout for a little over a year and eventually switched back to QWERTY. I had the same problem that many other people had with alternate keyboards - it's great if only you use only your own computer(s). Whenever you have someone else use your keyboard or you use theirs, you have to remember to switch physically (for them) or mentally (for you). You can argue for maintaining both layout proficiency, but what's the point of an alternate layout if you have to continue to practice the old one. I also never really had a health problem typing in QWERTY and Colemak didn't solve that (non-existing) problem.

Also, so many things are built with QWERTY in mind. Games default to WASD and some don't even have the option to switch. Shortcuts are created with QWERTY and are sometimes awkward to change (vim) to match the design goals of the shortcuts.

All in all, it was a fun experiment. But seeing as I don't have any RSI/other hand reasons to switch, it's not worth the extra effort to use.