Here are the list of notable changes:-

1. A light interface then Vista.. Looks better then Vista
2. Ribbon interface(aka office 2007 interface) in Wordpad and Paint.
3. Some changes in looks of startmenu
4. Calculater UI changed.
5. A new term Libraries is introduced which is equivalent to My Documents
6. A few changes in Windows explorer's toolbar.
7. Systray icons setting option in Control Panel
8. Few more options in control panel like Locations and Other Sensers, Credential Manager and Biometric Devices.
9. A better Theme options for windows
10. Homegroups are there.
11. Some display setting changes as posted in Windows 7 Engg blog
12. Games updates in Games Explorer
13. Some changes in Windows media Player also
14. New improved PowerShell