I've had no trouble at all with my '13 35i. The wipers work just as well as they have on my previous BMWs. If there is that much difference, take it to the dealer and have them take a look. It could be a bad sensor or the adjustment wheel on the wiper arm is not sending the proper signal.
The issue I've always noticed with the auto wipers is they don't always do well when a light mist or drizzle is falling. Rain is no problem, but mist has to accumulate quite a bit before wiping, since the system works by 'seeing' the amount of refracted light. If the drops are not big enough, there is a longer delay before the wipers fire.