Long story short, it’s awesome. The most significant change is that there is a hard level cap on your pokemon (even ones that you have caught yourself) based on the gym badges you have. So before you beat the first gym, the max pokemon level you can have is 20, and the gym leader has a team of 6 level 20 pokemon. This is actually sort of roughly analogous to how my brother and I used to play the pokemon games, with the self-made restriction that each pokemon in your party had to be within one level of every other pokemon.
This means you really have to consider type advantages, train up appropriate guys, and not just brute force the whole game with one pokemon. I’m having a blast so far. Turns out pokemon with a couple important rules tweaks is actually super sweet (and it was pretty sweet before).
There are also a few more very nice quality of life changes such as:
1) Experience is gained much faster
2) There is a built-in 3x speed option
3) The game shows your EV’s if you’re into that (I’m not that hardcore)