I am a big fan of Portal as it is, and when I saw this picture, I was quite impressed. The style is wonderful in my opinion, and is well executed. The darker color scheme is especially attractive, and gives a much more serious atmosphere to the pic than the normal Portal color scheme does. It is much better than the half-assed (not necessarily on DeviantART) art I've seen of Portal. The fact that you also drew an action pic instead of a simple pic of Chell stationary adds to my wow factor. I don't really have anything else to say, other than keep up the good work!
this picture really talks to me. the aerial part of the game is one of my favourite things to do, and the way Chell moves in the air really brings back all the good portal fun I've had. plus, the background looks great, all broken down and eaten by the plants, broken stuff everywhere... this is really good