I've used that before. Props to the developer, but on top of the extension, we also have to install software for it to work. It also doesn't fix new profiles opening in the background and the messing up of dock icons, although this might only affect Mac users.

The annoying thing for me is that Firefox already has a similar UI button that could easily be adapted to switch profiles. It even looks like Chrome's, but all it does it show you your Firefox/Mozilla account.