I was upset it didn't have ACC, but I actually have grown to like the Dynamic Cruise Control. When I was traveling in Germany (with European Delivery) i used it probably 80% of the time i was on the Autobahn - great way to slow down as well.
We met with the M5 engineers in September and airflow was main reason it is not on M5 (according to them).
2007 M6 Convertible
2013 M5 (9/7/12 ED)