As a Microsoft employee I have been using Windows 7 since the early internal betas. I have been impressed with the operating system (OS) since day one and it has improved with each iteration leading up to release. There are some nice, obvious user interface changes that have been made. Many of them are obvious, while others, not so much. The problem is, it is easy to load up a new OS and just keep using it like you did the old one. Same menu clicks and shortcut keys. In my role as a Windows Platform Engineer I sometimes get caught up in all the technical benefits/improvements in a new OS without really digging into all the new features. I used Windows Vista for years and did not become aware of several new features (e.g. calendar publishing/subscriptions, Windows Meeting Space) until I was studying for a certification exam.
To get the most out of Windows 7 head over to Tim Sneath's blog and review "The Bumper List of Windows 7 Secrets". Bookmark it. I have been back to this site 4-5 times. Block out 30 minutes and try each of new features. I guarantee you will find some you did not know about that you will end up using everyday (e.g. Windows Key +P). Here is a list of my favorites by number (you will need to visit Tim's post for the details). Leave me a comment and let me know if you found Tim's blog as useful as I did and the number of your favorite.