I didn't mind the random encounter rate of IS at all, because fights rarely lasted more than literally 10 seconds, counting the experience screen. Go in a battle, everyone's turn order is already set how I need it to be, auto-battle, win, back to exploring. In EP to accomplish the same thing, I have to spend at least 15 seconds in every battle setting the turn order first, then more for abilities. Then if the turn doesn't finish the battle, for round 2 I have to do it all over again. Suddenly the encounter rate hurts, and hurts hard, because it adds a whole lot of repetition to a game system that didn't have it in IS PSP.
I'm not going to lie when I say it's the main thing blocking my desire to pick it up again. I feel like I did when I tried getting through Persona 1 when I think about booting the game up again.