It’s also true that third-party patches have caused more problems than they solved. Even Jesper’s excellent VML protection script caused problems on a certain class of Windows computers in a common patch scenario.
But with the official warnings in mind, I feel that any company with a knowledgeable administrator who has the time to test a third-party patch or fix thoroughly can benefit using third party patches and advice in times of crisis. Some of these sources are quick to respond if something does go wrong: Jesper made updates to his fix-it advice as soon as he became aware of the problems, for example; ZERT appears to be making the right choices in how it applies its patches, not modifying the original impacted executable.
In my opinion, if a widespread exploit is high risk in your environment, you should consider testing and deploying a third party patch or fix. Management should be made aware of the nature of the third party patch, the risks, and give final approval. And as with any new patch -- even official patches -- you should test thoroughly and have a tested reversal plan in case the medicine is worse than the disease.