Earlier today on the official Call of Duty website the PC requirements and detailed enhancements were shown in a community blog. These requirements and enhancements are as follows:

Requirements

• OS: Windows Vista SP2 or Windows 7
• CPU: Intel Core2 Duo E8200 2.66 GHz or AMD Phenom X3 8750 2.4 GHz
• Memory: 2GB for 32-bit OS or 4GB for 64-bit OS
• Video Card: Nvidia GeForce 8800GT 512 MB or ATI Radeon HD 3870 512 MB
• The game CANNOT run on Windows XP

Enhancements

• The Black Ops II engine: "builds upon the Black Ops engine with a number of improvements including performance optimizations, enhanced graphics, and proprietary anti-cheat technology."
• The game engine has been moved from DX9 to DX11. The DX11 requires less CPU time to do the same amount of work as the DX9. A "quality over performance" option has been added to let the player customize his Black Ops II experience

  NOTE: these benefits still extend across many GPUs, not just DX11 hardware

• The PC version also features enhanced graphic quality. This enhances: " lighting, shadows, antialiasing, bloom, depth of field, ambient occlusion, and other enhanced effects that are still in the works. And the game can run at higher resolutions and higher framerates on the PC."
• There will be no framerate cap unless the player wants to enable one

The entire blog and information can be viewed here.