I will give Girardi credit, he has used the DH position incredibly and he could be the influence for more teams to utilize it the way we have. It requires, a manager to have a lot of flexibility, similar to the situation an NL team needs because they do the double switch when they change pitchers...(although for a different reason).
It is easy to see how it gives a team more flexibility to have an extra player/pitcher because their isn't one person slotted in as the DH everyday.
I believe this will be highlighted more as interleague play happens each day of the season next year....when there is more discussion all the time about interleague situations.