I say it's a keeper. I really liek the effect and the gradient in the sky as well... In terms of cropping I might be tempted to make it a panorama with the negative space either side as a feature rather than something that detracts from the image.
Personally, I like it just the way it is. The gradient effect of the window at the top and the large empty spaces add up to a heavy sense of suspense. They combine to add a lot of drama to the subject. Fabulous shot! Definitely keep it!