I think that the new rules will speed up game play. "How?" you may ask. Well, we are all familiar with the fact that game play speeds up as games move into the later turns. Why does this happen? Because we have been removing models on both sides as casualties. Fewer models on the table means faster game play.
I believe that 6th edition, being a deadlier gaming environment, will remove models faster and reach the quickened late game pace earlier. All of this entails our having become very familiar with the rules and comfortable with them.
Time will tell. I am off to read more . . .