Surprisingly, while the changes are subtle, they have really done quite a bit. The entire front clip is brand new. I really like how they have changed the grille to a single piece, compared to the previous that had an upper silver lip that lifted with the hood. The hood has also been smoothed out and streamlined, much better than the original IMO. The bumper looks worlds better, much more aggressive, and it has a bit more of a flow to it. The headlights have been smoothed out as well, the bulge towards the outside edge is not as pronounced as the previous ones were.
If you notice, this refresh begins to tie some of the new 7-series cues into the 3-series. My guess is so that it doesn't look dated when the new 7-series comes out. (smooth hood, 1-piece grilles, etc.) I would have preferred to see the coupe clip put on the sedans like on the M3 sedan, however, this is a compromise that is nice enough.
Again, much better than before.