Here are some of the changes that are being discussed as being a part of Windows 7:
New version of Windows Media Center
Gadget for Windows Media Center
Native support for multiple graphics cards from different vendors in one system
Gadgets integrated into Windows Explorer
Pin and unpin items...
calculator
gadgets
graphics support
installation
internet explorer
localization
media center
multi-touch
networkingapi
performance
security center
start menu
system tray
taskbar overhaul
user account control
virtual hard disk
windows 7
windows live
xml documents