This is one of the nice things I am glad they fixed in Windows Vista, but I hope they do not limit it to Vista, it would be nice for them to update it so you can postpone to a convenient time. Its annoying! Check out Automatic Updates in Vista screenshot:
I have a lot of windows open right now, working on a lot of stuff, this definitely means, I am not in the mood to restart my computer. Obviously Microsoft should realize this, it is my decision if I want to restart or not, now leave me alone!