MAXIMXYGO  Absolutely no changes whatsoever, besides renaming a Zimblet from "yahoo maps" to "yahoo local." Yahoo plans to (and by all appearances does) operate Zimbra as a separate entity, most likely injecting ZCS components into their online webmail offerings. I know it freaks some people out that Yahoo owns it now (why I don't know... yahoo's turned out to be a pretty respectable company these days), but I (nor other zimbra employees) can see any benefit from Yahoo changing anything about it, nor from killing it outright. It's a truly unique Exchange competitor, and makes its owners decent money... they only benefit from serving their existing target audience better.  
(Version 5.0)

MAXIMXYGO  Quite simply the best collaboration suite I've ever set up, administered, and used as an end user. The openness of Zimbra really makes it shine beyond the already *amazing* set of built-in functionality. It works wonderfully with iCal (subscribe/publish), WebDAV for "briefcase," plus a TON of other killer features, including an iPhone-optimized interface for mobile devices.

It not only acts as a very cost-effective "replacement" for Outlook, it bests it in every way. I have users using the native AJAX interface, users attached via IMAP using Outlook, Thunderbird, and Apple Mail and MobilMail (iPhone), even a few using the chat functions via Jabber in iChat. It all just works, and works *wonderfully.*

Top notch software. The Open Source version is great and FREE (that's what we use), and the Network (paid) edition is stellar, and very inexpensive.  
(Version 5.0)