I've rendered with shadows since the beginning, coz it creates depth and mood. I find that my renders will look 'bald' or 'default' when made without shadows...:) It's not always that a shadow fall exactly where you want (you can adjust using spotlights, if you're patient enough :), but even unexpected shadows can really make a cool effect at times. Perhaps the challenge in creating shadows is in making it logical...:) The easiest is to blame it all on the 'outside of the camera' source hehe, I've been guilty of this countless times, but a logical shadow & light combination will undoubtedly create magical images :) Just me two cents...:) Peace!