RAT 5,
it is a while ago, so I do not have the exact numbers present. But on the DH8-300, a standing takeoff with all the implications You describe was required in my company when close to the MATOW of the day. Whether it helped a lot or not, I have not verified, but still initial acceleration was noticeably higher. As was cabin noise; it only started to subside a bit to the normal rather high level when above letīs say 30kIAS.
On the -400, a standing takeoff just requires the aircraft to come to a standstill on the runway before setting T/O power (which is to be reached before 50kIAS); no running up the engines against the brakes required any more and still is the basis of the performance tables, although only explicitly required in low visibility operations any longer.