Interesting words Rainboe and Nigel on Draft about rotating and not waiting to fly off the ground.
There is a danger in hauling the nose up to an attitude and hauling the plane off the ground...while this may give you the test pilot's performance scenarior, the real world often has little dangers like contamination on wing (ice/snow) or a myriad of other things that can make things go wrong.
every flying attempt is imperfect...there must be a "fudge factor" or whatever you guys on the other side of the pond call it.
so be careful out there.
by the way, we were taught on takeoff if the stall warning/shaker etc activated to go:
firewall power
flaps 15
that simple and the plane will fly ...if the slats weren't out there.