Having been there, and spoken to locals it's seems very mixed.
Some think it's great for businesses,shops, restaurants etc and also go and watch the shows themselves.
Some just hate it but never really said why.
Another said the volume of traffic in the City centre is massive, thanks to the fringe ( which I found a bit baffling as most of the shows are in and around the Royal Mile and a few on George Street so never known anyone to take a car or drive from show to show as you just wouldn't get parked).