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.
including Vanadium?