I agree about driving in the city - but any foreign city : best to keep it to the bare minimum. Find a parking ground as close as possible to where you want to be, and forget about the car until you depart and pay the fee. IMO cities have become too hectic, and you have to be a local to have the proper wits.
Today you can use navigation apps like Waze and Google Maps to help you quite a bit - but they're still not enough if you don't know a city well, not to mention if it's a first time. It's not the navigation part that is a problem, it's just that almost everything is a bit different : the traffic lights, the signs, the roundabouts, the turns, the driving nuances, and the stress involved in having sometimes to make a quick decision in unfamiliar surroundings. I use Street View ahead of time to get an idea of what's waiting for me - and hope for the best.
Driving outside the cities and in the countryside : from my experience (in the northern parts of the country) the complaints are completely exaggerated, and there's nothing to be stressed about. The most you can say is that you might see some drivers take what I call "calculated risks" when driving - but if you use common sense and obey the speed limits and signs, you'll have no problem. I'd even say that drivers are courteous and rely on eye contact if a problem arises while driving. Having a rented car while traveling has a lot of advantages, Italy no exception, and if you consider yourself a capable driver, then don't let stories deter you.