Some sharpness is nice, some is not -- I have a ZeroImage 2000 that gives me really nice images that are actually pretty sharp, but soft in a pleasing sort of way. This is in a 10 by 10 inch enlargement.

A lot depends on whether the pinhole is really round and also whether the pinhole is the right size for the lens/film distance you are using. Too small a pinhole gives you distortion, too large and you get too fuzzy. It can get quite complex if you let it. The image itself can also sometimes look sharper just because of what sort of image it is.