Did you use fpdns (http://code.google.com/p/fpdns/) to finger-print Amazon's service? If so, I've never heard good things about djbdns :( NSD (http://nlnetlabs.nl/projects/nsd/) seems to be the new hotness as far as authoritative DNS servers go.
I've used NSD once, it was good. Other than djb 'non standard' conventions and installation procedures, I see no other issues with his software and am happy Amazon opted for djbdns, especially since I don't have to manage it :)
For another example, the DNS already has a standard update API, but Amazon chose crippled software and reinvented the wheel instead of interoperating with the dynamic update code that is already out there.