Cool to a degree - if anyone on here is as cool as Isaac Hayes then I'd be interested to know about it.  He made a vast amount of outstanding music, much of it highly influential.  (Remember he was also a musician and arranger at Stax.)  Shaft, for all its defects, was one of the first and greatest of the blaxploitation era films, and the soundtrack is one of its major strengths - without those amazing grooves Richard Roundtree simply would not have been as cool.  In fact, the opening scene to Shaft is the greatest music video ever made, and it was before music videos had been invented.  (No wonder the film goes downhill from there, it would have been impossible to get better.)

Also, Isaac Hayes took a starring role in Truck Turner, a blaxploitation film that's also a very good film (unlike most blaxploitations which are great for music/clothes/ghetto footage but often lacking in plot and other essentials). 

I'd say cool without qualification.