Also, I almost forgot...
Since Pokémon are now visible on the overworld, how does getting new Pokémon to spawn work. Like, say you're in Mt. Moon, and you don't see a Clefairy, and you want one. How do you get one to show up? Will the Pokémon just fade away over time and be replaced with different ones if you just leave them alone? Will you have to leave the room entirely and come back in for a different set to spawn?
And similarly, what happens while you're trying to capture a Pokémon? That is, once you go back to the overworld from "capture mode," whether you're succesful or not, will the same Pokémon still be there? Does trying to catch a Pokémon itself reset which Pokémon are available in the room, or is everything otherwise just the way you left it? And if the latter, what happens when you catch everything in a given room? Will new stuff show up on its own if you just sit and wait, or do you have to leave the room and come back in?
Going to be very interesting to see how that all works and it's the answers to those kind of questions that made me nervous about the idea of having Pokémon on the oveworld as opposed to random encounters. I hope they found a way of making it work well enough, but I would be lying if I wasn't nervous about what the exact implementation of that actually ends up being.