This sort of thing is hard to quantify. Certainly, from my experiences (I have an early 2007 X3) I do experience hesitation - particularly from a standstill. It's worst if I'm driving at speed towards a junction - then stop at the junction completely. Then, I depress the pedal to go again, and there's a real 2 second lag before the car actually starts moving. When it's on the go it seems to be fine.

I did say this to the dealer when getting a service earlier on in the year and asked for an upgrade to the s/w. They told me there's nothing wrong with it. Hmm...