Well, that was short. I had high expectations on this one, since I loved the first one. Unfortunately, I'm left with disappointment. It's not very bad overall, but I felt like it could've been much better than this.
Design-wise it's more or less good. Some segments are pretty fun, although it's a bit sad there isn't much new stuff compared to he first one. That's what I meant by it being a bit disappointing: this is pretty much The Castle 1 with some graphics changes.
Aesthetics-wise, both good and bad: I liked how the ? blocks have been animated, as well as other good elements. Although most of the times the BG was really confusing to me; also some palettes were very weird, like the flames (you can see them in the first screen) and the Mario palettes.
-Sometimes you can spot sprite tile limits issues; good thing it happens rarely atleast.
-The music breaks hack in accurate emulators.