Now I get back from a holiday in Crete, in a week approx. I drove 700 kilometres in the countryside, in the city, on the mountain, everywhere. The traffic is slow, no aggression, everyone is paying attention to each other. Very safe.
I've just been in Crete, and was surprised about how good the roads were, in fact everywhere, even up to tiny mountain villages. There isn't much traffic, and the greeks are driving just as carefully as here in Germany. Goats on the road once in a while is not a problem, everywhere in the world you should be ready for something or somebody being on the road.
I've driven that highway and there was absolutely no problem. But: Watch the speed limits, there is radar and cameras everywhere, you'll get caught speeding.
Hi - see all my tips in my article: www.zigzagonearth.com/driving-crete-rent-car/ - including that Driving is on the right side, and that most cars are manual - wishing you a great trip!