@PopeDai: The blog post says they WILL NOT be adding CalDav or CardDav. The current state of affairs is confusing, but I gave up on Gmail back then anyway. The reversal of arguments regarding CalDav and open vs. closed makes me see red, but I could really care less about CalDav support or even Gmail support now.
An official blog post from late January says they will: ( http://blogs.windows.com/windows_phone/b/windowsphone/archive/2013/01/30/synching-google-services-with-windows-phone.aspx ) and I can't see anything in Mary Jo's article that contradicts that.
Note that I'm talking about "pure" CalDAV and CardDAV, not Google's implementation.