I'm going through all of the maps that I played for the contest and post my rating and comments.
It may be a bit out of date if you have updated your map since then, but hopefully it's useful feedback nonetheless.
judging comments
||Aesthetics: 3
well detailed overall, nice use of space. Good texturing. Lighting is well balanced, but a bit bland. Room design and texturing look a bit sloppy, especially in the big space with all the test chambers. (One chamber is suspended in the air; the outside of the area is one large box.) Also there is a strange white rectangle on the wall in the office area. (Missing texture?) Some misaligned brushes here and there.
Gameplay: 4
Completing the antline connections with cubes is a good puzzle idea, and it is introduced well. Some small technical problems keep it from getting 5/5: the dropper in the side room became unusable the first time I played, and there is some weirdness with the tractor beam, when the player or cubes get stuck against the fence.
Difficulty: 5
Gradually progresses from easy to medium. Well suited to introducing a new puzzle type.
Other Comments:
Nice use of Wheatley character vs the moving / exploding environment. The ending is surprising and creative, if a bit of a downer 
Personal score: 4||
So after reading the others' comments, I now understand that you have to think without portals to get out of the office area and into the last test. In the contest version of the map, you can still place portals on the wall in the office, so perhaps that needs fixing.
Also, I don't know what the deal is with the missing texture, but I've seen that with a lot of contest entries. I'm beginning to think that those Steam workshop problems around the time of the deadline may have played a role in that.