Many users hate having to restart their computers because of how time consuming it is. Besides it being time consuming, it is also frustrating because the reason we are restarting it is because of a problem we’re having. The Microsoft Windows Vista restart manager will shut down only the application that needs to be shut down, and then perform the installation which eliminates the need to restart your computer after everything that you install.
Of course, Microsoft did not stop there because they also implemented a ‘smarter’ standby system which will only take a few seconds to go into standby and will make the system feel like it is being restarted, so that you don’t have to restart it as often.
News Source: The Unofficial Microsoft Weblog