The single most visible change in Windows 7 is the new "dock style" taskbar, which shows icons instead of buttons, with all application windows combined within a single button. I'm quite certain that the very first question many people will have is "How do I turn it off?", and this video will show you how.
I strongly urge you to at least give the new Windows 7 taskbar a try it takes a little getting used to, but it's really a nice move forward. Does the new "dock style" taskbar work for you? Tell us in the comments.