Average speed cameras seem unbelievably dangerous to me. I haven't ever driven somewhere with them, but I suspect all I'd be thinking about was the speed limit, resulting in very dangerous driving. With all my focus on making to correct average I'd fail to properly track other drivers and potential hazards.
I'm much happier with a flow of traffic enforcement. Ticket those who speed excessively beyond what traffic is generally flowing and let the posted limit be more of a guideline.