Kensais, Weapon Speed factors, and attacks per round

Perhaps someone can clear this up for me:

I was considering making a Kensai to later dual to a mage but i didn't want to focus on a typical boring weapon like a long sword. It occurred to me to me that due to daggers having a speed factor of 0 that a fighter with a grand-mastery of daggers and two weapons style should attack faster than any other possible character. Is this view correct or am I mistaken as to the effect of a weapons speed factor?

Further as grand mastery of a weapon confers a -3 bonus to speed factor is it possible for a grand master dagger user to operate at a negative speed factor or is zero the fastest possible speed.

In other words is there any benefit beyond novelty for me to use a dagger kensai as opposed to a more traditional weapon choice?