Yeah, it's almost completely unnecessary - if you drive with due care and attention. My 500 has ASR and you have to be doing something very stupid to get it active - and then, the effect is not smooth but instead a vigorous bumping
In theory the ASR could work more effectively than the driver - in practice it doesn't.
I drove my Stilo Abarth on a track (standing start laps) and tried switching ASR on and off. With brutal foot planted driving the ASR gave a faster lap time than with it off, but with normal control of the vehicle (i.e. a degree of mechanical sympathy and smoothness), whether ASR was on or off made no difference.
I tested stability control the same day. With the brutal driving (standing on the brakes in the middle of a corner) I could feel the stability control intervene and save the car from spinning. With normal control I was on the limits of adhesion most of the time and the limitations of the car's rather poor dynamics (Stilo, remember) were far more apparent and the stability control didn't intervene or help.
Therefore, it is my belief that stability control doesn't improve the capability or performance of a car, but it does make it able to be controlled even by a ham fisted driver. I think in an emergency situation, we've all been ham fisted at some time.