I think part of it is that people worked really hard to update their anti-virus. The anti-virus definitions have been available for two weeks, and, with the attention this has been getting, people just made sure they were up-to-date for it.
I don't think this is an isolated incident. After Microsoft patches this one, Windows users shouldn't be fully confidant.
This is a significant situation. Anytime you have no patch available, it's a dangerous situation... We'd rate this as critical.