I have only one real issue with this game. The health upgrade on Potal is hidden behind a fake wall. It's obvious that there's something hidden in that building, because there's nothing there, not even furniture, but up till then the game has trained us to use the reveal potion to find secrets.
I had to look up a guide to find it. Why not make it a secret door that can be revealed by the potion? This is the one part of the game that I would say is badly designed.
There is something else I think you missed, however: there should be more NPCs that react to potions. Throwing a reveal potion onto the invisible guy on Potal, throwing a freeze potion onto Movo on Meztla, and another one I can't remember right now, should all get reactions.