Bill has watched me sing for many hours! You must get pretty close to the mic and keep the gain up when using most pa systems so that feedback is minimized. Particulary with the keyboard vocal harmonizers, gain and proximity balance is extremely important.
Also, it helps to use a hyper- or super-cardiod mic.
Now, recording and radio work is a whole 'nother story. You have a guy on the mixer to adjust, add or detract whatever your voice needs. Just be sure the guy knows what he's doing!
BTW, I must be pretty bored to be spending the week in Atlanta, GA and take the time to post on here!
Oh yeah, don't let anybody you wouldn't French-kiss use your mic.
DonM