It is a reference. Secretariat is a pretty well-known racehorse who, in his most famous race, ran every quarter mile faster than the last. He was accelerating the entire time, in other words.
I think this is balanced because few people have a need to go quite so fast and on most maps there isn't enough open ground to stay in a straight line for longer than a few seconds. It comes out to being a short sprint ability, in other words.
Also, there are already some pretty wild perks in-game, especially in the two-handed tree.