We have integrated our Open and Active Directory environments. We use AD for all authentication, and GPOs for managing the PCs, while using OD to manage the Macs. It is working pretty well so far, although on occasion a Mac will unbind itself... and we have some issues with forcing password resets/expirations. We still haven't quite nailed down printing, as it asks for authentication anytime they try to print through the Windows print server, but we can push printers out to the Macs using the printer's IP.