Here you can read the most notable new features:

http://blogs.msdn.com/tims/archive/2009/01/12/the-bumper-list-of-windows-7-secrets.aspx

For further information, you will find here a good walkthrough:

http://www.howtogeek.com/howto/the-geek-blog/what-you-should-expect-from-the-windows-7-beta/

A very simple, but interesting feature is called Aero Snap. In my daily work, I often have to compare or to analyze information from two different windows. With Aero Snap, I just move the first window to the left side and the second window to the right side. Aero Snap automatically splits the screen and arranges both windows.

Another very nice feature is the history in the new taskbar. Every icon in the new taskbar opens its history with a right click on it. With this feature, you have a fast access to all recently opened files for a specific application.