The Uber drivers I have used have all been great.
Under Dutch law taxi drivers need a number of additional courses and successful completion of the certifications associated with them. In addition they are required to be screened for previous convictions pertaining to alchohol- or drug abuse, traffic violations, and inter-personal violence convictions.
There's no 'uber' in the Netherlands, just 'uberpop' which is an illegal taxi-driver with none of the training and none of the safe-guards 'normal' taxi drivers have to conform to. 'Uberpop' is promoting illegal taxi services.
Taxi drivers in the Netherlands behave themselves because the first DUI means they will never drive a taxi ever again. They don't beat up customers because they will never again, ever, work as a chauffeur, not even on a freight lorry. Run a number of red lights in a few years and you'll lose your VOG and with it your license to drive a taxi.
We used to have an America-styled mob company in every city. For instance: the TCA, Taxi Criminals Amsterdam, required large fees from its drivers, to protect them from 'damage' and to assign them rides. Heavy-handed law-enforcement did a lot of good. Uberpop seems to be determined to re-establish the New York-style cabbie from the late seventies.