As a chiptune fan (and game developer), it's hard for me to comment unbiased...
The OST is not groundbreaking, but it is original. By maintaining its chipmusic origins, but also elaborating upon it, the tracks feel as a finely tuned and positively different soundtrack for a NES game.
However, all tracks could use a bit more flair and variety. At times they seem a bit monotonous and fail to make good use of the variety of chipmusic sounds existent today.
I especially like the first 22 seconds of "Good Day" which could easily be used an intro for many things.
Lastly, is the game "Level Up" fictitious or is available?