Upgrading Windows 7 Ultimate to Windows 8 Pro: What features am I going to lose?

• Shadow Copies / Previous Versions (replaced by File History)

• Universal Spell Checking

• Natural Language Search

• Multiple Clipboards

• Windows Explorer (command bar is gone and replaced with a ribbon UI. Now referred to as File Explorer)

• Windows Update Desktop Notifications

• Windows Desktop Gadgets

• Flip 3D

• File Manager tab support

• BSOD details & technical information (screen look changed)

• Desktop Pen, Ink and Touch Input

• Windows CardSpace

• People Near Me P2P API

You can also check The complete list of features removed in Windows 8 Wikipedia article for all the details.

Some installed software might be incompatible, The upgrade assistant will give you a list after scanning.