Excerpt from my car manual, quite cool, short and nice description why some people return STi's back to the dealer after few weeks of driving:
"Because your WRX STi is a performance machine above all else, the driving performance of your WRX STi has been prioritized above driving comfort, which can sometimes result in higher NVH level (noise, vibration and harshness) under certain circumstances" (source: 06 Owner Reference Guide SUBARU IMPREZA WRX STi)"