I go with David Arbogast about using the function.
Personaly I only use the C1-setting to be studio-prepared.
For pictur style I leave it on portrait since I mostly do that.
Once I experimented with boosting up the sharpness from 3 to 7 and it was horrible, really terrible result.
Even the proposed setting 3 is just slightly too much. The best result, IMHO is to leave it on 1 and post-sharpen with PS (when required).
Greetings from Ghent,