I'm talking about hosting your own external DNS stuff. In this case you control your destiny with regard to changes, and can be exactly as responsive to your internal needs as you need to be, which is a good thing.
On the down side, it's an extra server or two you need to maintain on your DMZ, or on your security perimeter. Additional administrative overhead is generally rather minimal, because typically all you want to have in external tables is probably A records and MX records for your mail servers. Typically a ISP should carry an A record for your firewall, or external router anyway... You wouldn't want internal DNS records visible outside.
Just looking for more pro/cons from people....