Start blender -> sel cube and enter in edit mode -> Subdivide (Number of cuts 3) -> Face select mode -> sel one face -> press Ctrl+Shift+Alt+F -> in last used operator window we see that sharpness equals 135.000 and linked flat faces are select now.

Then deselect -> sel one face -> 3DView -> Select -> Select Linked Flat Faces -> and in last used operator window we see that sharpness equals 0.000 and whole cube are select now.

I think menu tool must have the sharpness equals 135.000 like hot key tool.




Platform:
================================
Windows 7 Home Premium x32


OpenGL:
================================
- Renderer: ATI Radeon HD 4770
- Vendor: ATI Technologies Inc.
- Version: 3.3.10362 Compatibility Profile Context


Blender:
================================
Version: 2.56 (sub 0)
Revision: 34552