Yea, I thought of the storing too much crap on top aspect, but since I really don't have any other place that I can easily have a clear workspace to work on guns etc, I end up cleaning my rifles on the kitchen table and my Fiancee hates that (even though I put down towels).
I've also heard that you shouldn't put fluorescent lights above the workbench, because they emit too much electrical noise/interference that can screw with the accuracy of digital scales. Not sure how much truth there is to that, but it'd be pretty easy to test with a set of calibration weights.