System Information
Win7 64bit | GTX580

Blender Version
Broken: 2.73.9 51a60cb

Short description of error
I think currently it only happens when painting in UV/Image Editor. In 2.71, it is almost fine, but it became more obvious since then, especially when painting with smaller radius. Turning off the peassure button will "solve" it temporally.

Exact steps for others to reproduce the error

2.72+:

2.71:

Thanks for checking.