Definitely an interesting shot. Works a bit better with more detail when clicking through to flickr. Properly exposing your subject, regardless of what it does to the background, is the right thing. Actually, I have seen some amazing shots with a properly exposed subject and dark backgrounds. Sometimes it helps if the subject is just a tad underexposed or if the contrast is low, but depends on how much you want contrast to make your subject pop vs have the tone feel consistent. Here, I think the GBH is still a bit overexposed, mostly in the highlights/whites. I would start by toning those down a fair amount and the overall image by ~1/3 stop. I'd probably drop contrast a bit until it feels better, right now it is pretty contrasty. I would also tighten in on the GBH, eliminating some of the blank headspace, balance by doing the same to the lower part of the picture. Symmetry is key to this type of image, so I agree with Jonathan, the log to the right needs to be cloned or cropped out, but you want the darkness to be uniform on both sides and, as David mentioned, I would have the GBH centered. Finally, and I get caught in this conundrum all the time as I love the vertical symmetry of a reflected bird in water, but I would play with losing some of the reflection. I am not sure if it is right for this image, but do not be afraid to try (I am sometimes so in love with it that the overall image suffers).

Overall, great shot, especially for a walk with your dog.