MacBook Pro (Retina, Mid 2012). I've done it, because Final Cut Pro demanded it. Regrets, because Photos.app is now severely broken and causes high loads to the point where my mouse pointer (or beach ball) freezes intermittently (which, in my opinion, should be impossible on a modern computer system). Can't really process photos now. Extremely shameful work from Apple there.

Finder bugs have been persisting since Yosemite, with a very common one where drag & drop stops working until Finder is force restarted. APFS conversion went well and problem free. Even homebrew survived (mostly).

Strange USB problems persist, but they seem to be hardware related and ever present on this generation machine (first one with USB 3).