I use CC3 to make roofs and some shadows, the ground texture is added in PS.
My notes:
-Houses too uniform (try some different roof types)
-Roof color artefacts (those are a bitch, I've tried getting rid of them but I think it's down to rendering and rerendering til you can cut and pase the good buildings)
-Ground texture inside the city (render separate layers and use PS/GIMP to combine is my best tip)
-Effects (you have a lot of options for making good sheet effects that you might try out, but see above, try CC/PS hybridization)
-Layout too uniform (try breaking up the rows of houses a bit as you have in the SW corner)
Now, don't think I'm shooting your map down, It's a good first try at CC3, much better than my first attempts, even when i used Gandwarfs AWSOME tut!
Keep it up!