Windows 7 + Nvidia Geforce & OS X 10.10.3 + GTX 980
Broken: Blender 2.74
Short description of error
The new viewport AO feature is inverted. Any feature that sticks out is darkened, which cavities are untouched or brightened. This is in inverse of what AO should do, and the opposite of the AO feature in Cycles or Blender Internal.
Here's how it should look:
Exact steps for others to reproduce the error
Take Suzanne and enable viewport AO.