BTW "show stopper" implies something so impressive that it gets everyone so excited the show can't go on until people calm down. I think that's the opposite of what you mean in this thread. "Deal breaker" is more like it.
To the weather sealing question, the D600 appears comparable to D7000, which means rubber gaskets on all the doors, but in reality any camera with a pop-up flash has questionable weather sealing. It's not really possible to put a good seal on that door.