Neil's description of what's happening is exactly what I feel in the same kinds of situations. I've got about 1,200 track miles on my 1M so far this year. All of it has been at Road America or Blackhawk. I'm also using PFC-01 pads, Motul 600 and steel brake lines. One difference is that I am using either Grand-AM take off slicks or Hooiser slicks. I've also described the felling as a short hesitation as I trying to rotate the car.
At the ALMS race at Road America I got a pit tour and after the tour I got a chance to talk to someone from the product group at BMW NA. I told him I really liked my 1M except for the corner brake control still being on when DSC is completely "off". He was somewhat surprised that it was still coming on. He thought 1Ms were the same as E9x M3s and he thought it was off when DSC was off for an M3.
I offered to send him the traces from my AIM Solo DL that show opposite corner brake pad pressure when there is no pressure on the brake pedal. I didn't think he was interested in getting them.
I also told him that it would be really nice if the push to pass function was actually controllable and predictable. On this one he agreed. I told him it would be nice if it was a button instead of being activated with the gas pedal.
2011 1M AW, 2011 A3 TDI, 2013 Mini JCW, 2014 F150, 2016 Focus RS on order