Explorer:
Microsoft is introducing a new taskbar in Windows 7, some call it the Superbar, by default it comes disabled in build 6801 but ca be enabled. This new taskbar provides an easy way to access running programs and features the ability to pin programs to the taskbar, also programs are now represented by their icons and not their name.
Also, hidden programs do not extend to the side anymore but rather show in a small window. Also notice the small rectangle on the right? When clicked it minimizes all the windows to show the desktop.
UAC:
One of vista features, UAC (User Account Control) was either a loved feature or a hated one. It asked the user for permission to do everything. In Windows 7 Microsoft made UAC less intrusive, only asking permission to install programs. To run programs that make changes to the system it is necessary to run the program as an administrator by right clicking>Run as Administrator. UAC can be set to different settings for different protection levels.

Ribbon Interface:
Microsoft is implementing its ribbon interface in more programs that are built into the Operating System. Paint and Wordpad now have Ribbon interfaces.
WMP12:
Windows 7 includes Windows Media Player 12 instead of 11. WMP12 features a GUI change and still has some bugs as it is still in Beta changes. WMP12 integrates into the new Taskbar to provide Play/Pause, Forward and Backwards controls as well as mute.
These are some of the main changes in Windows 7. In my opinion Microsoft seems to be doing a great job on 7, mainly focusing on fixing the errors they made on Vista. By the looks of this Build it looks like Microsoft will be able to make the deadline, which is currently Late 2009 or early 2010. We can expect the first Beta build in Early 2009.
-OCM770