The Start button has been removed, even though it is still available as a “hotspot” in the lower left corner of the screen, and on the “charms” menu.
The Start menu has been removed in favor of the full screen interface called Start screen. So far I’ve yet to discover any useful registry entries to disable this menu.
The Aero Glass theme which has been featured in Windows Vista and Windows 7 has been cut out from Windows 8 in favor of a non-transparent Metro-style theme.
Microsoft Gadgets which has been featured in Windows Vista and Windows 7 has been removed in its entirety.
The command bar is no longer visible, and has been replaced by a new Ribbon UI.
Windows Explorer has been renamed to File Explorer.
Windows Media Center is not included by default in any version of Windows 8, but available as an add-on. (as previously covered in this article)
Windows Media Player does not provide DVD playback functionality, while DVDs will still be playable in Windows Media Center if it is purchased separately. (as previously covered in this article)
The POSIX subsystem, SUA, has been dropped.
Previous Versions has been replaced by a somewhat similar feature called File History.
The Blue Screen of Death no longer shows the technical information about errors and technical information (this must be found in the logs or dumps if required)
Windows CardSpace has been removed in favor of the new feature U-Prove.
The Parental Controls feature present in earlier versions of Windows has been replaced by the Family Safety feature.