I would be interested in this as well. I run an office that is currently peer-to-peer and mixed with mostly OS X clients and some flavors of Windows (2K, XP Pro) scattered in.
My boss is pushing to move to Exchange because of the group calendaring and Outlook integration that Exchange offers. I need ammunition!
Actually, I just need the right solution, whatever it is, and info such as Colin requested would really help out.
p.s. I am also looking for some real-time (in-person or on the phone) consulting on OS X server in cross-platform environments if anyone is willing…jtntATgmail.com