Using boom stands or hanging mics definately helps keep stands and cables out of the way more than straight stands. I prefer to set the (vocal) mic(s) so they are located higher than the singer's mouth and nose. Mic angle depending on which mic I am using at the time. This usualy forces the singer to "open up" their throat and increases lung capacity a little. This also helps remind singers to keep their hands off the mics, and helps to keep the propper distance for the mic to do it's job best. There may be better reasons but these are the main reason I like to suspend vocal mics, especially with inexperienced singers.