I must not be doing something right, because the only change I'm noticing is the handle turning gray.  I load the grayscale image in the Textures tab, go back to Materials and click the Spec button in the Map To tab but that's what it gives me.  

Go to Materails<Material<Spe. Then you can change the specularity color and levels. However, the specularity is further affected by the second drop-down list in the Shaders rollout.

It is better to do one thing well, than to do many things and excel at nothing.