Not a bad start. A few suggestions:
1) Set rings to Deaf. This makes them hover a little bit over the ground. They look a lot better that way.
2) Take out those pointless floor spikes along the side of the mountain. They're killing the framerate.
3) In several places you seem to underestimate the power of the springs. There's a yellow spring at a jumpable height from another platform, and there's a red spring where a yellow one would suffice. Test the springs to make sure they don't go too high. In general, jumping can get you up 100 fracunits, yellow springs can get you up 416, and red springs can get you up 1024.
4) There are some sector closedness errors here (sectors are supposed to be closed polygons, some of yours aren't). It's probably because of linedefs that have the wrong front/back sectors. Check the raw linedef data and see if you can fix that. (Ctrl+K in WadAuthor will show a list of errors; the "Sector x is not closed" errors are what I'm talking about.)
5) It looks like there's only one path through the map so far. Adding multiple paths will increase the level's replayability a lot.
I mostly like the design so far, though. It's very nicely laid out.