Inspired by this post, I just installed Firefox on my iMac. Here are two problems.

1) After a vanilla installation, I clicked the profiles icon. (It's the person in a circle button.) When I click it, a popup menu shows, then it relocates north 30 pixels, then it redraws where it is supposed to be. For a software with a main interface only having 8 buttons, it is bad that one of them does not work properly.

2) I'm at work right now so I planned to migrate from Google Chrome and uninstall it. I successfully migrated my work profile. I don't see a way to use a separate profile for personal. Tried Command-Shift-M (Chrome shortcut to change profiles) and got nothing. That ended it for me.