I ever rented in different occasions a car with them at MXP and also with the infamous Goldcar that is the other one offering the cheapest rates, so far never had any issue, BUT you need to know how to deal with them:
always book directly, never through a broker
better to buy their policies to reduce CC deposit and deductibles to zero
In such way you can still save quite big money comparing to global renters without worries of being ripped off at the end of your trip. Even with extra insurance their rates are same or even cheaper than basic rates of famous rentals and you're totally covered in case of any accident/damage.
On the other side I have myself seen how they often try to threaten the customers and push to buy their special covers when they just purchased the basic/cheapest fares or bought via brokers (that also sell their refund insurance not recognized by rental company), I can also believe of some of the horror stories you read about them trying to overcharge charge for previous damages, thus important is to be aware of what you're doing.