I recently updated my server to 7.2.1, and it looks like calendar seems to be working for me without having to perform contortions.
I am also able to add the carddav account, but when I open up Contacts and try to sync, I get "Some server contacts could not be copied to this address book.". If I look at the console logs, I see a multitude of:
2012-12-11 2:59:43.706 PM Contacts: [CardDAVPlugin-ERROR] CardInfoFromVCardData(): Ignored vCard /dav/MY_ACCOUNT/Contacts/ because vCard is empty
2012-12-11 2:59:43.707 PM Contacts: [CardDAVPlugin-ERROR] -_handleAddsOrModifies: could not parse vCard in /dav/MY_ACCOUNT/Contacts/
Has anyone run into this before? I don't know where to even begin with this.