The pitch here appears to be that this can allow communication between services without having to add them to a tailnet or such; e.g. if you wanted to let a friend or coworker access some service on your local network without making them join a tailnet, add a public external endpoint to forward traffic, set up a VPN, etc.

IIUC you just send someone 'here is the connection information' and it just works automatically.

Yeah and my understanding of Iroh wasn't quite right either, it sounds like it's positioned to be more of a library to use in code, rather than a VPN solution like Tailscale.

I love MagicDNS - A long time ago I wrote a stupid Python script to have it continually generate MagicDNS names until one of them contained a word I was looking for.