R2 also allows you to see pitcher stamina, pitcher confidence, pitch sequence, and slows down the pitcher. The last one is the excuse used by people most often, which I don't personally need. You can pitch as fast as you want to me.
I do use R2 a lot, but I only hold it for a fraction of a second and 99% of the time I've already let go by the time my opponent has selected a pitch, even if they're going as fast at the game allows.