I really liked this level. The overall concept isn't particularly original, I thought (multi-layered city, exploring because of boredom/dissatisfaction, etc.), but the details are.
This level is consistently funny without trying too hard (like basically any DEtM clone). Jens Jensen's casual incompetence, the occasionally-helpful cats, the Society for Not Jumping Off Roofs, etc. are funny without being intrusive, which is good. The level makes me want to play part 2, as well, which also is good. (Though the "end of part 1" sign at the end, with no win tile, was kind of irritating. I know the intent is probably to let the player go back and explore more, but it makes the level feel like a beta.)
[Begin ruthless criticism.]
However: technically, this level has some problems. The water in the sewers and elsewhere is layered inconsistently (that is, for example, you can be standing on a piece of ground, and yet be in front of a layer of waterfall that is going in front of the ground, leading to a PARADOX). This isn't remotely game-breaking, but it happens in a lot of levels, and it always irritates me. (Also: you can stand in the same tile as the fishing Knytt, and yet be in front of him, leading to another PARADOX.)
In the sewer area with the blue castle tileset thing, there are many solid fiddly bits (like the tapering points on the edges of some platforms, and the little piles of broken blocks on the ground) which are irritating. (With the tapering point dealies on one-tile-tall platforms, it's easy to run under the very edge of one, jump and go nowhere, then have to reposition yourself a bit to the side of the edge to get up.)
Other than these things, there're no significant errors. There's a blank sign in the zoo, but that's really about it.
[End ruthless criticism.]
So: I enjoyed this level (which is certainly above average for a first level), and eagerly anticipate part 2.