Actually had this discussion Friday night.  Someone had seen where they had run the tile right up under the downspout, right next to the house.  Put a 6-4 inch reducer on(4 inch tile) and covered the 6 inch 'bell' with hardware cloth or something similar to keep leaves out.  I think he said the screen was cut to fit inside of the reducer.  The downspout went straight down, no curve and not connected, so you know if it is plugged or not.  Sounded like a good idea to me.  Ben