I have heard from a fellow administrator about how few technical support calls the help desk has been receiving since switching to Zimbra. While I don't know all that much about the product I have a few questions before I can seriously ponder migration to it.

1.) Is there a way to transition/convert mailboxes and calendars from Exchange Server 2003 into the latest version of Zimbra?
2.) How nicely does Zimbra play with active directory?
3.) What kind of hardware would I be looking at for a dedicated server with 50 users needing Zimbra? (I would prefer to utilize an OS like Ubuntu or Fedora)
4.) Are there other administrators here who have purchased the mobility connector for blackberry? How well does this work for you?