I have three 3-hour sessions under my belt (excluding Character Creation which was done separately). I came from 5e, but I have a long experience with RPGs, beginning with the Rules Cyclopedia. I will try to limit my comments to what I have actually experienced (except for a bit at the end).
Our group is running Fall of Plaguestone. We have 4 characters: elf wizard (my character), half-orc paladin, halfling rogue and elf alchemist.
Overall, the system works pretty well. Combat seems to go pretty smoothly. The half-orc paladin and elf alchemist seem to be working as intended.
Like a couple of others have posted, the wizard is underpowered. To compare with 5e (I am also running a 5e game), at the same level, the bard feels like an integrated member of the party even when he does little damage. I can see his cantrips making the monsters miss, and his spells buffing his allies or debuffing his foes. My wizard cantrips are doing scratch damage each turn, and so far, not a single spell I have cast has had much of an effect. Plus, I feel I am locked out of the 3-action system since each one of my spells takes 2-actions to cast.
Maybe it will get better as we level up, but Plaguestone only goes up to level 4, and frankly, if by level 4, my wizard doesn't feel more effective, I will probably drop the character, if not the game.
The other thing that I hate (but kicks in more at higher levels) is the skill system. When I DM, I like to throw my characters curveballs in the form of skill checks they are not trained in. I find it is neither realistic nor particularly fun for the barbarian that dumped Charisma to be able to avoid Charisma checks for the entire campaign.
This doesn't work in Pathfinder 2. By level 5, an on-level DC is pretty much impossible unless you're trained in the skill. If I use the Simple DCs instead, the trained DC is ludicrously easy if you are trained.