Now all you need to do is get a 2013 535 loaner so you can do a direct comparison to your car. Really curious to hear how the car both feel since your description of how the 528 drives sounds like how my 2013 535 drives. I wonder if it was possible for the dealer to load in the 2013 engine and transmission software into a 2011 car to solve all the delay problems.
Current - 2013 N55 535xi Msport SAT
Retired - 2009 N54 335i Msport 6MT
Retired - 2000 M52TU 323i ASA Supercharged 5MT
More photos of my car here