We had an incredibly smooth launch with Windows 7. There's been one issue that keeps coming up that is incredibly easy to fix...
If your taskbar and windows are not being themed but your icons and wallpaper are, 99.9% of the time you need to do this:
Go to "Control Panel" -> "Appearance and Personalization" -> "Display". Ensure that the "Smaller - 100% (default)" radio button is selected. Then re-apply the theme. You have it probably set to medium. It has to be set to Smaller.

