Things I liked:
-- the use of the 6 city "attributes" means that one can easily express a great many different types of conflicts. A bardic whisper campaign against the king, a religious revival, a plague, or an influx of black market goods flooding the city, or a clash of knights on the field of battle can all be modeled with relative ease.
--The core system is simple enough that it can be added in easily without overwhelming the players or the DM.
--I liked that different races all added something special to a community, and come with their own special buildings.
--the added mini-adventures, random encounter tables, and terrific artwork make this product feel very professionally done.
Things I disliked:
-- Cities grow virtually automatically with only a minimal effort on the player's behalf. Given enough time, it seems every inconsequential hamlet will become a great metropolis. This doesn't really require the player's to do anything heroic, and feels unsatisfying to me.
--Almost no use of money. For some this might be a small point, but as 5e has limited uses for large sums of money. Allowing players to dump gold into a town seems like a no-brainer to me.
--Too much direct player control. The rules make it appear that the players select each and every building that appears in their town. I feel like a city should have more of a life of it's own rather than being so directly controlled by the players.
--Without the DM frequently modifying the rules as presented, things can often be extremely illogical. A town can have it's commerce reduced from a thriving hub of trade to near ruins, and in a single season bounce back to full again. There's no real reason you cannot have a full blown Metropolis in the middle of a tundra, as the rules don't make growing a city here any more difficult than usual.