All of the existing versions of Windows, excluding Vista, were designed with no thought at all to security. As a result Microsoft has been running around in sheer panic terrified that the hackers would get ahead of their ability to issue patches. These versions of Windows were just plain unsalvageable because of the design decisions that went into their consturction. So a whole new operating system, from the ground up, was needed.
Vista has tons and tons of stuff in it to prevent hacking or make it a lot more difficult. It is not impervious, but it has a whole lot of high level brain power poured in to tighten it up.
Are we going to continue to see Microsoft patches? Sure we are, but hopefully the underlying software is a lot more secure.
I would expect it to be shaky at first, then it will settle down and work just fine.