Weird...I asked and was told, "No break-in period. Just drive the way you normally drive."
Well, today's technology may be good but it is not that good. Anything new needs a bit of breaking in. The rings take a few hundred miles to get seated properly. That's one of the reasons gas mileage and performance improves a bit after several hundred miles on any new car.
So, no matter what "they" say, treat your smart "gently" for the first thousand. Probably most important is to vary the speeds - for example, don't keep it at 60 mph on the Interstate for a hundred miles the first day you have it.
