Very nice old-school map. Just as a personal design preference, I like to try to add multiple entrances to dungeons (and to different dungeon levels), as well as plenty of "loops" within any given level of a dungeon to make the dungeon less linear. I recommend having a look at Justin Alexander's series of posts on JAQUAYING THE DUNGEON, there is some really great dungeon design theory to be had there.

Cheers,
-Arsheesh