Hope you all don't mind me playing catch-up. I didn't have much time to play this weekend.
MAP03:
Well, this was a pretty standard facility-type area (which I suppose is why they call it "The Oasis Facility"). Difficulty is a bit lower than the previous map, although I still died once to that archvile because I got stuck on a box and couldn't hide from him in time. Embarrassing. The outdoor area looked quite nice, but the indoor portions were less impressive visually.
MAP04:
This is a nice-looking level! I especially like the path to the gate at the beginning of the level. Two things I didn't like about the gameplay: 1) the annoying chaingunners that hide behind parapets until you think you've killed them all, then when your back is turned they unload on you, and 2) that yellow key trap! Just on the edge of being TOO devious for me. Ah well, it's still a fine map.