I really like the basic image itself quite a bit - well done.
As for the technicals:
White Balance looks a bit on the 'cool' side. I find that Canon tends to exhibit this under cloudy or low light conditions.
Regarding noise, it does look quite good as displayed, but I'd be interested in seeing one 1:1 crops, to really get a feel for the actual noise. As you know, when you downsample the image for web presentation, much of the noise disappears, so it ends up looking better than expected on the web.
That said, on my 1DMk2, I'm reluctant to go to ISO 3200, although I will if I have to. That's another reason I'd like to see a 1:1 crop, to get a feel for how much improvement they've made on the Mk4.