I have been working on implementing groupware solutions for years and finally got ZCS NE approved late last year, moving away from CommuniGate Pro, and have managed to dodge that 'big company's' elephantine solution.
We don't have everybody moved over yet, but we did do a hugely successful technology preview of the 5.0.1 web client (served here from an Intel Xserve) and the group, about 40% of the Chicago office, was extremely excited. Though I don't feel it is necessary to kill off fat clients, my boss is really pimping the web client to great success.
The product itself is a fantastic feat. Thank you everybody at Zimbra and 01.com!
P.S. Please say you guys are going to be around for a while!!!! Don't make me come out there!!! ;-)