I am a recent owner of a 135i and also had the procede for a little over a month. I must say I am very pleased with the result. The car is smooth and has effortless power. I have not experienced any issues or problems and Adrian has assisted on many occasions to answer any questions I may have.
I have let my brother who drives a stock e92 m3 take my 135i for a spin and he agrees the car has turned into an absolute weapon yet retained all its drivability.
I admit i have not upgraded my procede to the latest version as welll im lazy haha ... but will set myself up shortly with it and provide a review if you would like on my experience with auto tune.
In addition I may be wrong... if you get a powerchip ... it can be reflashed over by the dealer.... although i may be wrong on this.