NIS had it's day and was a good soldier, but keeping it secure has become a huge headache and the time has come to replace it. Since you already own Active Directory, you may as well save time and money and utilize it for managing your Unix network.
How do you manage Unix UID's, the numeric designation for a Unix account across your network? One customer had 16 NIS domains with at least 8000 users in each. UID's had to be matched with their AD user name and standardized across the environment before we could eliminate NIS and the threat it implies due to its insecurity.
Microsoft handles DHCP and dynamic DNS very well and is already integrated nicely with Active Directory. Iit usually makes sence to completely integrate DNS especially if you manage both BIND for Unix and Server 2003 DNS for Windows.
s!