I'd agree with most comments about the first and second screen Tracer, but I've got to say I'm impressed with the third and forth screens. I had to look twice, just to make sure they weren't from a UT2004 map or something, because thats the feel I got from them.
I like most of the texturing and brush work, though its a bit dark even for me
. The radioactive waste also seems a bit too bright for the map, but then again the HL engine seems to like making water textures glow in the dark. If your trying to fix that I found making the textures darker generally works, as I did in pegasus to make the water dark.
Generally top stuff though, obviously needs some more work in parts, but looking very good so far.