Does the DCAEK shorten the reset on the M&P, compared with the stock trigger?
Yes.
1/16th to 1/8th of an inch for reset length depending on how your trigger bar shepherds crook is bent.
http://www.youtube.com/watch?v=uohQeHxPFL0
Not directly related to your question but it does show the overall trigger throw on an Apex equipped gun.
Thanks.