Interestingly, it won't be /vital/ to install this patch if just about everyone else in the world does...like with vaccination, if everyone else is not going to get infected by whatever little beastie comes along in a few days to exploit this hole then it decreases the chances that an unpatched machine will get infected
That said, the speed with which people reverse engineer what hole has been patched by an update is such now that I'd rather risk applying a patch as soon as MS release it than leave a machine vulnerable for even 24 hours.
Also, I'm not sure everyone is aware, but as an example, the hole that Nimda exploited had been being used by hackers for a couple of weeks to get into all sorts of systems before someone kyboshed them by releasing a worm that alerted everyone to the problem. The exploit code that CodeRed used had been in the public domain for months before someone turned it into a worm.
With this latest patch, MS were informed of the hole months ago, so chances are that there are a lot of people out there who have already got tools to get into any machine they like (despite the supposed secrecy)...so, yes, I think this lot of patches is important. Others may be less so, but anything which allows a remote attacker to compromise a large range of Windows versions without involving user interaction ought to be patched asap.
Imagine that 4 lane highway with a load of people lurking in the bushes with keys to your car waiting for you to stop for a picnic...er...anyone know where I'm going with this analogy?
