Last week, we finished migrating 3500 users from GroupWise to Exchange 2007. Fun project and interesting experience to see the users and the IT folks shifting from an application they've been using for ages to Microsoft platform. From users’ perspective, we installed outlook 2007, and they loved it. It’s more feature-rich compare to GroupWise. There were few nice features in GroupWise that outlook didn't have, but the users didn't care about it that much. From the IT guys perspective, there were two groups, Group A, Pro-Microsoft, they like working with MS products and familiar with Exchange and MS clustering. Group B, Pro-Novell, let's say..... They rather stay on Novell for another 100 years! We've installed Exchange 2007 w/CCR in 2 physical locations. We also enable UC for all users and OCS for 400 users.
Microsoft-Exchange team are doing great job by simplifying administration and usability, and also adding great features and having it integrate with other MS products such as Office 2010, SharePoint, etc.