No manufacturer will say this in public, especially not BMW, but the break-in period is mostly bogus. The main reason they warn you about a break-in period is to ensure that IF the engine has a defect (metal shavings from the manufacturing process, for example), it can be detected early in the engine's life. If there IS a serious defect with the engine, though, that defect will make itself known whether you're doing 30 or 70.
Drive the car the way you'd normally drive. It'll be alright.
Juan