Turning off the light emitter property does speed it up, but it does some really undesirable affects to hair which I don't care for.  You are right though, turning that off definitely got rid of the smudgy shadow artifacts, but you also lose the affects that are beneficial.  I found that solution almost immediately way-back-when, but I like having the emitter on, so another solution was needed.

 Seachnasaigh:

No need to clarify my friend.  I didn't mistake it at all.  I just wanted to clarify to BB that I wasn't fussing at him.

:0)