How is this a replacement when it doesn't run OS X? I wish Apple would make a statement about the direction they are going with OS X Server. We have switched everything to Macs here and depend on iChat, Address Book, & Push servers and there's no way in hell I'm switching everything back over to Windows.
The writing is on the wall. We, like many other institutions, are laying plans to transition away from Mac OS X Server, because absent a definitive statement from Apple, the direction away from the server space is clear (any one-word emails from Steve Jobs on the immediate future of Mac OS X Server notwithstanding).