I owned a 57 plate s3 for around a year.
I had it remapped, it was f**king quick for a 2.0l, only thing i really raced that left me was a 911 turbo, top end was also good for a hatch (on a private road) i hit 170mph.
However, unless it is icy or snowing the quattro isnt much use, and down to the way the system works on the S3 it makes them understeer BIG TIME.
Bmw handling is more enjoyable and they feel more balanced.
I have owned 4 performance audis now and i can honestly say i will never go back.