I am about 6-7 hours in, about to start level 3.7
I've collected all 3 chests on each level and beaten each corresponding bonus level. 2 of the bonus levels were frustrating (mostly because you have to be perfect as there are no checkpoints), but otherwise are strong companion levels to the game.
I've loved everything, except the rocket controls, which I don't know, are broken or at the very least occasionally inconsistent.