I agree with neko, you have really bad halo effect on the trees esp in the foreground. Its alot of effort but it'd would be worth it if you remove this. I too like the POV, very dramatic, lots of potential, i think the building just looks very cg-ish atm.
-If those panels are corten adding bump and reflection will really help with blending.
-cheat some subtle tree reflections in PS on the glazing
-look at your colour balance, photo is very green, your building is harsh red and grey...i'd adjust one of them to match
-lighting is ok just a little flat, i'd have a stronger light source from the right mayb some godrays also note your shadows are darker than the photo.
This is a nice image and has potential to be very nice. Interesting to see a client prepared to hide even a tiny bit of his new building in favour of a better artwork.