(This page is based on a mailing list post by Matt Timmermans)
You just need to change the EMCMOT parameter in the [EMCMOT] section of your ini file from "freqmod" to "quickstep".
If your PERIOD was set too high because of CPU limitations, you can probably set it lower. 0.000015 should be fine unless your system is very special.
If your DEFAULT_ACCELERATION and MAX_ACCELERATION are set unrealistically high to reduce path errors at corners, go ahead and set them to something your steppers can really handle, since the new BDI has path error limits.
If you were avoiding backlash compensation because you were losing steps, go ahead and put it back in, since quickstep enforces acceleration limits while compensating.