Multiple sources have noted that Apple's DNS patch, at least on Mac OS X 10.4 and 10.5 client versions, isn't implementing the key feature that's meant to block cache poisoning: port randomization on requests. While the same version of BIND running on Linux systems behaves as expected, Mac OS X machines doggedly issue DNS requests on sequential ports, making them far more vulnerable to spoofing by malicious folk.
This may seem like an esoteric vulnerability, and indeed for most Mac users the more important question is whether or not your ISP or network manager has patched the primary DNS servers you rely on (you can check your DNS server status via Dan Kaminsky's tool here). The behavior of Apple on this security issue, however, is very troubling. Waiting weeks to issue a patch for a key vulnerability and lagging behind other OS vendors is bad enough; shipping that patch only to have the user community discover that it doesn't work worth a bucket of warm spit ... that's not the act of a company that claims to care deeply about the security of its customers.
Update: Kaminsky suggests that we lighten up; Mac OS X Server (which would be the most vulnerable to attack, if it serves as the primary DNS for your network) has been patched, even if the client patch isn't behaving properly yet.