Personal Experience 335d
I have driven this car on the track at BMW driving experience. I noticed it right away because it had euro front headlights, I almost ripped them off!!! J/K!
It was a bit louder than I thought, but it was definately fast.
I would say its 90% of the 335i in acceleration.
It makes the typical diesel acceleration noise and has the same minimal lag as the 335i.
I personally would rather have the diesel, because of the added fuel economy. The class directly after the driving experience told us it would get 30% better gas mileage and 26% less emissions.
I also had the opportunity to drive the X5 3.0d. That was pretty awesome as well. It was as fast as the 4.8is for sure.