Looks good to me. Try as I may, I can't see any signs of where you stitched them together. Nice job. Not sure if it matters, but I'd straighten the horizon, unless you were just using the image as a stitching exercise, then it's irrelevant.
Impressive amount of detail, even in the distant buildings. Look forward to seeing some of your twilight/night time city-scapes. The ones you posted in the fuji forum were impressive. Will be interesting to see how the sigma compares. I like to shoot similiar images, and was wondering how the sigma would perform.
Keep them coming.