I typed on Sholes keyboards (and typewriters) since the 70s. My typing speed averaged between 135-170 words per minute in US English.
I attempted Dvorak for about a day but the layout is not good for a Unix user as some of the digraphs are pessimal.
When I switched to Colemak, I had a tremendous amount of difficulty undoing 35 years of various habits, good and bad. My first month, I probably averaged about 10wpm. I sent a lot of very short emails and was frequently frustrated.
Finally, my speed became "reasonable" and then I made an even more useful switch. Why bother with changing around the keys on keycaps that are still arranged as if they are driving levers through an inked ribbon onto paper? I looked for "matrix" keyboards and bought a Truly Ergonomic. Aligning the keys with my fingers, wrists, and forearms makes a lot more sense than continuing to follow old design constraints that are harmful for a large number of people.
Now I'm back to typing at a speed where I don't have to wait for words to appear on the page (any more than usual). It's much more comfortable and it's comfortable for a much longer period of time.
As for going to foreign computers, a) it's optimizing for the uncommon case, and b) Colemak is supported by almost every major OS and takes less than a minute to switch on Arch, Windows, or OS X. I do miss it on the iPhone or iPad on-screen keyboard, but it's supported on external keyboards.
 I'm not sure I'd buy it again as even the "silent" model is too loud for me. In addition, some of the punctuation keys are in annoyingly odd places and need to be remapped. A number of even more extreme ergo keyboards drop the staggered key layout as well.