Personally I can see myself using this to access my homelab from work without having to open extra ports. Since I can't install a personal VPN client on my work machine, a web-based desktop behind a login would give me most of what I want.
Guacamole was actually my first choice and it's what I used a year ago. In that time span I've screwed up enough that my lab actually needs a whole rebuild, so I'm looking at alternatives to see what could be swapped over. As it is, I think Guacamole remains my first choice. I was just responding to the question of what this could be used for.