Chad,
you may receive as many opinions as if you ask about motor oil
My experience is this, the trans shift "should" be fine with any fluid. I have run type "F", Dexron, hydraulic fluid, and "race fluids" and seen no significant difference in any of them. (we are talking about medium horse power, foot brake applications)
These days I run Dexron/Mercon type lll because it is easily available and performs fine for the above mentioned application.
I suspect your "less than firm shift" is not fluid related.