Oh, my. I just set up Zimbra on my iPhone 2.0 software with ActiveSync. Verdict? Angels are descending to bless the experience.
It will sound silly, because Windows + Blackberry has had this functionality for eons, but it was such a wonderful thing to be able to accept appointments on my phone, have everything automatically synched with my Zimbra server, etc. It's not, in other words, a giant leap forward for email and collaboration, but it's a major win for Zimbra.
Thank you, Zimbra. Thank you, Microsoft (ActiveSync). I've joined the 21st Century. :-)