one minor annoyance is that there's a max limit to the ControlPath string (seemingly due to there being a max path length for Unix Sockets) which I've occasionally hit when connecting to hosts with very long hostnames (AWS default hostnames can sometimes hit it, IIRC).

Also note that the docs recommend against using publicly accessible dirs such as /tmp/ for storing your mux sockets. I'm not sure of the exact threat (maybe just info leakage about what hosts you're connected to, since the socket permissions themselves are strict), but I use ~/.ssh/mux/ for mine.