Ed Bott has posted an excellent list of 10 tips and tweaks for Windows Vista that could help the more advanced users do what they want with Windows Vista.
One of my favorites, as with many others here internally at Microsoft, is #5: the ability to create a System Health Report. This report will help you diagnose your system’s health and provides possible solutions issues that may be affecting your PC’s health.
Another expert, Andre De Costa, has also posted a few Windows Vista tips of his own. His latest talks about where the Run command went (i.e., it's easily displayed on-screen by using the Windows key + R key sequence)...very handy.
I look forward to seeing more of these tips and tricks for Windows Vista as we move past RTM :)