I know myself and others have observed that the F30 seems to sit high at the front - well at least on the pics of brand new cars that I've seen.
Just came across a couple of 330d M Sports on BMW AUC and they certainly DO NOT seem to be sitting high to me. They are both on 19's, but wouldnt have thought that would make any difference as the overall diameter of the tyre is the same as 18's.
I can only assume that after 3-4 months the front end settles down at bit. They both look good anyway....