Some haloing around the roof edge, also the highlights in the centre of the image don't look right - there's a sharp drop off in luminosity around the second post of the handrail. It's a shame, because otherwise it's been beautifuly processed with wonderful tone and colour. Compositionaly it's spot on as far as I'm concerned. With a little bit more due care and attention I would have expected to have seen this in the top 5!!! It may still do well!
The magic wand tool is very good at selecting areas of differing contrast, also if you're finding it difficult to reduce halo's, try feathering only by 1 or 2 pixels and then using the clone stamp tool on darken! i.e. alt + left click on the adjacent sky, then left click on the roof (which is considerably darker) and then proceed to run along the halo whilst you hold down the left mouse button - it should do a good job! This method only tends to work well as in this example where there's a high contrast between areas.