As for the software issue -
I bought my E90 at FLOW BMW in Winston-Salem, NC. I liked the "lock-after-takeoff"(doors automatically lock at 5 mph) feature and the daytime running lamps of the E46. When I asked for these features in the E90 they said it would require a software upgrade. The car was so new it didn't have those features.
They did upgrade the car's software, and were happy to do so. BUT they did say they were also RELUCTANT to do so - because if it ain't broke, don't fix it.
Please bear that in mind when you PUSH for software upgrades. An E90 is a blend of computer and sport car. What if the DSC or DTC fail when you need it? All because you are constantly tinkering with your car? You CAN do more harm than good by pushing for software updates.
If BMW feels the software updates are necessary - they are going to install them no matter what when you service your car. Count on it.