I'm now to the fourth world (ignoring the cosmological nitpick that worlds should be in galaxies instead of the other way around). There has been a tremendous variety of settings, obstacles, and characters thus far. The boss of the third world is one of those that is challenging enough to take a few tries to beat but very satisfying once it happens. The fire flower is better this time around from how I remember it in the first Galaxy game, although you still have a time limit on it. The new power-ups for Mario and Yoshi are all excellent.