This is a decent level. It feels like a compact Gaia.
Like Gaia, I think this level spreads itself too thin. The wide variety of environments is impressive, but none of these environments is particularly well-established. As StaticRomantic mentioned, many of the area transitions feel kind of arbitrary. Most all the transitions located to the right of the starting point are pretty good, but the ones on the left feel odd. The sewer/red planet one is especially random. There are also a few places where the tilesets (and environment) just change when you enter a new screen, which always comes across to me as sort of lazy: there's no real transition, just a quick change. In those places where there is an actual transition where the environments almost overlap, the transitions are handled well, however.
Overall, I was disappointed that the custom object use just dropped off more or less totally after sailing on the pirate ship. The custom objects that are used, though, are used well- they work to establish the environment rather than just draw attention from it with their novelty. I was also disappointed that there were so many unenterable buildings. The whole city area felt shallow to me, because I only got to see the exteriors of the buildings. I especially wanted to enter the castle in the sky, as the area surrounding it feels like it's building up to the castle- but then I get there and the doors are locked.
There weren't many bugs I found. I only found one outright SGE (see attachment). On the pirate ship, when anchored at the city area, the enter and exit sounds for the door to the bar are wrong: I think the enter sound is like the default shift sound, and the exit sound is the switch. The wind-wallswim effect thing under the floaty cloud area ends with Juni trapped in a solid cloud, with no escape. (Maybe this is deliberate.) There were a number of things that felt "off", though, without being actual bugs. Being able to walk behind the queen bee, after having walked in front of all the worker bees, was weird. In the city, there was inconsistency in whether doors and windows had sidewalk in front of them, or the sidewalk sloping off before going in front of the door/window.
The plot felt rather tacked on, and was a lot like Gaia's plot. (Neither plot ever really goes anywhere. Probably. I didn't find an ending in this level, though, so maybe there is a conclusion to the plot. I found two secret areas, one of which had a key and a symbol, which I took to imply there was a secret ending.) Also, though the opening cutscene says the planet is called "Myrsomething Grottglufs" or something, when one returns from Niffanne Beta, it calls the planet "Earth".
So. Although I did run into all the aforementioned little wrinkles in the level, I enjoyed it. The music fit the areas well (or at least didn't jar with them), and it was neat to see some tilesets that haven't been used much.