[mrmekon]

Apparently, according to this thread, WebDAV is alive and thriving.

CalDAV and CardDAV are certainly alive, but I think they're in a pretty horrible place.

I run a Radicale server, which seems very nice, but configuring clients is a nightmare. Every client seems to require different settings, and work to differing degrees.

The native Contacts/Calendar apps on OS X were the worst. They connect, work for a few hours or days, and then permanently break. I have to delete and re-add the accounts over and over again until eventually the same settings suddenly work, and they work for some hours or days, and then break again.

Thunderbird consistently works, as does Android's DAVdroid, but other clients I've tried have been almost-hit-or-completely-miss.

emacs –– EMACS –– has terrible support. This might not sounds like much, what with it being a text editor and all, but this is exactly the sort of place where it usually has 15 different implementations, 2 or 3 of which are really nice. Instead, it's riddled with XML parsing errors, the biggest CalDAV client deletes all of your TODO entries, and there doesn't seem to be a single CardDAV library. I take this as a sign that those protocols are not being widely embraced.

That said, when they work they are truly fantastic. I don't particularly care about the underlying protocol, but I pray that CalDAV and CardDAV support gets more consistent and more popular.