I agree that the cast is better than 1 and EP but I can't say the plot is better than EP. To me EP had weaker less interesting characters than the teens from IS but the plot was much more cohesive and interesting than the one from IS. I was also much more excited to know what was going to happen in EP. In IS when you clear the dungeon on Mt Iwato the plot becomes a mess.
The gameplay is good and balanced if you know the ''correct way'' to play it. You must learn which contact information will make demons give you tarots, items and which one will make them flee. This way if you are lost in a maze and low on MP you can get cards, items or get away and walk around to regain MP. It's a good way to collect free tarots which you can use to summon every personas by painting them. Random encounters can be cleared in one round if you know which fusion spells to use. And here lies the weakness of the game, it's grind heavy. Every 2 dungeons or so you have to switch everyone personas because their stats and skills (or both) are gonna be outdated. You then have to grind to raise these new persona ranks so you will unlock their spells. With no spells and no fusion spells you're pretty much dead. And this repeats itself again and again.
Some dungeons are also frustrating expecially those with invisble pitfalls :lol .I played IS again during the summer and I still love it but like P1 it's clearly not for everybody.