And the user experience is pretty seamless. However the backend management of the Mac using Active Directory isn't there. (e.g. group policy, logon scripting would be different, et-al)

Not to say that you can't centrally manage UNIX based systems using LDAP, but as another person pointed out, why would you go that direction if you were already vested with Windows (unless of course you were running NT4 in which case the pain of going to AD versus LDAP is about equal)