According to everyone I've talked to about this, the patch itself is trivial to apply. The only known complication is that it may slow down DNS for heavily used servers.
As I type this on Thursday, July 31, there's still no patch from Apple. Even if one comes out just after this article is posted, it would still be almost three months since Apple was first notified of this issue. In that time, Apple has been the only vendor not to release a patch or clearly communicate the reasons for the delay to its customers. Unless you have back-channel contacts at Apple, you have only been told the standard "Apple takes security seriously" line, if you were told anything at all.
To put this into perspective, less than a week after launching MobileMe, Apple had not only apologized to customers for the problems with that launch, but issued extensions of service to help make things better. When Apple customers had some problems with consumer-grade e-mail and calendar synching, Apple took nigh-immediate action. Yet, given months of lead time on a vulnerability that makes every unpatched Apple DNS server dangerous to anyone using it, there was nothing. No mea culpa, no "here's what we're going to do to fix how we respond to vulnerabilities in the third-party products we use in Mac OS X to make sure this never happens again." Just the standard "we'll tell you what you need to know, when you need to know it, and you'll like it" spiel from Apple. This is not a major update to apply, but Apple will be the last OS vendor affected to release a patch. Yet, Apple has managed to make major fixes to MobileMe and release an update to iTunes.
There is no level on which Apple's conduct here is acceptable. It speaks of a security-vulnerability review process that is broken. It shows that either Apple is completely unaware of what is going on with the software it bases its OS on, or that the company knows, and just doesn't care, because after all, iTunes users are having problems. Even if the patch is released today, that's not going to be enough. Because if the underlying process is not fixed, this will happen again. And again. And keep happening until it causes Apple enough pain that it finally fixes the process.
Apple needs to not only release the patch, but issue a public mea culpa that apologizes, and outlines the way the process(es) that allowed this to happen will be fixed. If that does not happen, then as an IT professional, I will be required by my own professional ethics to begin a serious review of any uses of Apple hardware on my network that faces the public Internet, and see if those machines can be replaced by a similar product from another vendor that not only claims to take security seriously, but actually takes the actions to show it does. I would recommend that anyone else in my line of work do the same.
In the last few months, Apple has, by inaction, silence, and arrogance, shredded the security goodwill it had earned over the last few years. It will take years to regain that goodwill. Ask Microsoft how hard it is to regain goodwill once it's gone.
The worst part of this is that had Apple not "been Apple about it", the entire problem would have been a non-issue. Instead, it's made a mockery of Apple's claims of being responsive to security issues. I sincerely hope the Windows team is trash-talking the heck out of Apple and OS X over this, because in this instance, it's absolutely justified.