Operating system and graphics card
Windows7 gt560; Windows8.1 HD4000
Broken: (example: 2.69.7 4b206af, see splash screen)
Broken: 2.76 48fdd6
Short description of error
When option is checked it sets "Enable tablet pressure sensitivity for strength/size" checkbox for all brushes. Its similiar bug for size and strenght option.
Exact steps for others to reproduce the error
Based on a (as simple as possible) attached .blend file with minimum amount of steps
Check Unified settings: size or strenght, cycle throuhg brushes and look how it affects "Enable tablet pressure sensitivity for strenght/size" checkbox.