Very nice level. There are a number of things I specifically liked: I liked the tilesets, and the unity they gave to the level; I liked the subtle but effective deployment of custom objects; and
I liked the extremely subtle hinting at the location of the first secret (I only noticed it on the way back), and I liked the neat effect used at the secret ending.
There wasn't much I didn't like. Having to go back through areas I'd already beaten was sorta irritating, but not really a problem. I didn't like the lack of any real setup; there's one intro screen showing the ultimate goal of the level, but then no explanation as to why Juni (or the player) wants to get there, and Juni just starts standing in the (apparent) middle of nowhere. I also didn't like the fact that the level is more or less totally lifeless- other than Juni, I didn't see any animals, which felt weird. (Maybe that was deliberate, though.)
Overall, a well above-average level, though.
Incidentally, it's possible to stand on the spikes without danger (see attachment). This is so close, though, that it'd be very hard to exploit.