The subie Tuner that I use has asked me many times if I want to have a tune of the stock ECU but with my K&N and custom exhaust they tell me the hp improvement would be minimal. They have extensive knowledge of Stinger but have moved to Atom or Link if I remember right and someone on the Quebec side has a spyder that they did up with and Atom ECU. They find them much more tunable. The owner of the shop holds multple rally championships and sells all over America. These were the guys who advised me against believing anyone who said they could get over 200hp with a stock NA. 
In any case, for an owner who wants to turn the key and go, and cruise, it is a solid option and what is not to like about the torque curve and drive by wire.
Carey had a suggestion on changing the pedal sensor curve, so I bought a module to vary the curve but the ECU kept throwing a code and going into limp mode.
So if you do not like the rheostat stock ECU throttle positioning and response, you could get a tuning package for the stock ECu to allow you to modify only that parameter... a bit expensive but dooable.