I switched to Colemak, and I am also forced to use qwerty on a lot of keyboards. Colemak is very similar to qwerty, so its not that big a switch. Mostly the r/s location is the biggest issue.

Besides that, it's worth mentioning that there is an executable that you can use for Windows machines to easily switch to Colemak without installing it on the box. I carry it around on a thumbdrive, place it on a network share, and keep it in my Dropbox. I can always get to it. So 80-90% of the time I can use Colemak, and I am reasonably fast at qwerty when I can't.

The reason I switched (like the OP, if you read it again) was to reduce RSI pain/fatique. It's worked wonders for me in that respect. I'm not that much faster, so speed's not a major incentive to switch, IMO.