Now that I think about it, there's also some other things I use it for. I embedded the Tailscale API into my VM manager waifud (https://github.com/Xe/waifud) so that I can pass a `--join-tailnet` flag to `waifuctl create` and plunk new virtual machines onto my tailnet with Tailscale SSH enabled. It makes testing things on arbitrary versions of Ubuntu so easy that it feels like I'm cheating.
My hypervisors are also subnet routers so my VMs can connect to eachother like they're on the same network. All the fun of static routing without any of the "fun" of static routing!