DNS Management Solution for ISP

[geekgrrl at geekgrrl.org]

I know this question has been asked before, but I thought I would ask it again with a slightly different variation. Those of you who manage dns for ISPs (as aopposed to single domain/single IP block type companies), what sort of packages, tools, or scripts do you used to manage DNS for both your organization and  your customer needs? The ISP that employs me has been evaluating a series of commericial packages that consistantly seem to turn up some sort of bug or lack of feature that makes them incompatible with our current processes. How have others solved this issue?