Thanks I am having this exact same issue, as well as hard shifting between 1-2 when things are cold. Driving me nuts because I love everything else about the call (well, except the push-button gear selectors). Haven't wanted to deal with the run-around from the dealer on this yet, but it's getting to the point where I think I need to. The long lag when you hit the accelerator hard when rolling slowly could definitely cause an accident. I have come to expect the lag and try to avoid situations that cause it, but every time my wife drives the car with the kids it makes me nervous.While checking a different hunch by @Hodna and driving in sport mode, I identified a way to recreate the issue every time. This should help me greatly in communicating the issue to the dealer.
The issue is actually the gear shift between 1st and 2nd gear, but only when the pressure on the accelerator is released briefly and then pressed again. i.e. if you keep steady pressure on the pedal while shifting from 1st to 2nd, there is no issue. If, however, you start to accelerate in 1st, then let off the gas pedal, shift to 2nd and hit the pedal again there is a significant lag time before the throttle responds.
Once I discovered this sequence in sport mode (because who wouldn't let off the gas while switching gears if you were driving a standard?), I changed back to regular Drive mode and continued to create this issue by letting off the accelerator briefly right after starting from a stop, around 5mph or so, and then trying to punch the gas again.
I'm so excited to at least be able to recreate the issue on demand, and appreciate you all's advice and help it took to reach this point. Have the appointment at the dealer for next week so will let them know how to create the issue and see what they say.