I always update as soon as one is out. I must admit, that there have been one or two that I wish I hadn't downloaded, but in general, I haven't had any problems. Haven't had any problems with the Blaster Worm either.
As Storm said, I too, wish everybody had downloaded the Blaster update. My firewall gets constant hits and even my ISP was down last week for almost 24 hours because of this worm, and it's one of the major ISP's in the US. You would think they would have been protected by now.
Also very important to keep your anti-virus and firewall updated regularly.