GCFreak, I must say, you have horrible tastes in levels.
!!!, the level is FAR too cramped, and is almost maze-like. There are no alternate paths, there's nowhere in the level where you can actually get going fast, and there are no places where any of the characters' abilities are useful. You seem to have learned the technical aspect of level making (Using linedef specials, adding a thok barrier, using texture offsets, etc.), but the design of the level is just bad.
Sonic levels are meant to be open, allow for a little exploration, have secrets and multiple paths, and be easy to find your way through (That is, you don't ever have to stop and search around for the correct way to go). Just look at the levels from official Sonic games, or some of the levels in SRB2 or the level packs for it. Those will show you how to make a good level.