It's mainly different wheels, and some other small things. Such as a Bose sound system (Which I have heard is the same as the standard one really), driver information system (screen near dials) and a Concert radio (with a sound AUX input).
However, because of the upgraded wheels, they tend to ride higher than normal A3's. Have you considered a 1.2 TFSI Sport? Give Drive the Deal a ring, I'm currently using them, and they have been excellent uptill now!