I drove a Mazdaspeed6, and hands down there is no comparison. Always on AWD, it shifts power to the wheels that grip almost in anticipation of your next move. It is the soul of the WRX with the body of an executive. I added a blow-off valve. and turbo gauge so I knew what was going on under the hood, and 12-15psi at full throttle is what awaited. I get no lag with the new valve and even an extra couple miles per gallon. I may add sway bars to improve cornering, though a strut tower bar is almost out of the question given the arrangement of the intake.
Besides the stopping power and control STi shorthrow is the best part. Low profile hood scoop is functional and stylish without being overbearing. No spoiler is necessary, though the chrome plated rock panels are worth every penny. They add even more style to this already stellar looking vehicle
Forget AUX input on a stock system, I would be fine with being able to replace it. Lack of a kit results in a whole crazy conglomerate solution for integration with the stock radio. A big hassle for those who want AUX or something beyond the stock 6CD (no MP3).