i've been using it for a few years and love it. Started out as a way to keep my to-do and task lists organized and accessible from more than just my phone (f-droid tasks/astrid app is amazing, too). Then I started using the calendar side of it when I started to move away from google crap.
I still need to wrap my monkey brain around reverse proxy so I can access it externally.
Oh, and I wish it had a webdav component for some more fluid file backups and sharing.
Add Tailscale to your server, and either add it to your devices or enable the Funnel feature (which funnels specific traffic to a specific service in your Tailscale network).
I run Tailscale on every device that supports it, and use one device on my home network as a Subnet Router (as the name describes, provides a route to it's subnet for Tailscale clients to have direct access to that subnet and it's devices, eg printer or other hardware).
I love to see people using WebDAV/CalDAV/CardDAV! They’re great protocols. I’m building my own server (I’ve only gotten the WebDAV part done so far), so maybe I can learn from their setup process.
I just wish it had a built in way for normal users to share read/write individual lists and calendars. Afaik you have to kludge it together with symlinks.
But then again, any users would also then need multiple accounts for read/write share if you don’t want everyone seeing everyone else’s stuff
My partner and I have each our account, with private calendars in, and a household account with the shared calendars in. It's not perfect, but it works for a small group