Windows 7 x64 & GeForce GT 740M
Short description of error
In this new 2.73 version, sometimes I see some kind of flickering of material color in viewport, and I'm not sure, but it has something to do with opening projects started in Blender 2.72b.
Here is a saved project, that if you select one of face in front of you, you will see that other faces are getting darker
Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps