Just because BMW call it a Sequential Manual Gearbox does not make it a sequential gearbox. It is a conventional manual synchromesh gearbox with an electro-hydraulic system to change the gears in a Steptronic fashion. A true sequential box (dog box) is a totally different animal, and I am not aware of a dog box ever being sold in a standard production car. As explained in this video, a true sequential gearbox is a specialised tool for racing, and although superior to a synchromesh box in virtually every way, the noise of straight cut gears and the abrupt shifts are not suited to production car use. A dog box does not need the incredibly complex control and operating system of the SMG or DCT, but the latter certainly appears to have achieved a performance level that keeps M car drivers happy
I looked long and hard at getting a sequential box for a previous car, but considering the cost and the fact that the car was not a dedicated race car, I gave the idea away. For an average punter such as myself who does not do track days, a Steptronic auto with a flash is plenty good enough !!!
Cheers...