I was looking at the pricing for the paid version of Zimbra, and I'm not quite seeing where a small busines (say 3-20 people) fits in. For larger installs, per user cost is under $30. For smaller installs, we're talking from $483/person per year for a 3 person office down to $96/person per year for a 15 person office.
Given the fact that OS-X is now supported, it seems like a lower price point for small offices (which just happens to be my bread and butter) combined with the tiny Mac Mini would make an ideal Exchange killer. $600 for the mini, another $100 for an external FW drive for backups and you've got a nice Zimbra server/intraweb server/backups server/print server.
Are there any creative licensing plans afoot?