There's this one traffic light intersection close to where I live. Road is uphill at about a 6% slope. If I stop on red, then when light turns green I have to press the accelerator what feels like a couple of inches before there's any response (horns honking behind me), then the car takes off like a rocket.

Had the major IMA recall done late 2010, I would say this symptom began after that. Sorry, I can't say what SOC was (although usually 4 squares), or number of bars of assist when it takes off. I'll pay more attention next time.

 

I've had similar issues a few times with a SOC below half (especially after the latest software update) starting from a dead stop on a hill but maybe not quite as dramatic as what you have described. Without any torque from the electric assist, between the tiny gasoline motor and the CVT being a bit sluggish to get the engine revving high enough, it takes a few seconds to get the car rolling even with your foot smashed to the floor. Try monitoring the Assist gauge, I bet in those cases it doesnt give more than 3 bars of assist and only for a split second at that...

 

I own a first-generation HCH, and do this for different reasons, but have you tried shifting into S when starting from a dead stop on an uphill? I find it helps. Once I am up to speed I shift back into D.