Have somebody hold a flashlight at different levels pointing down at you while you lean into the mirror and imagine that you're trying to get an eyelash out of your eye. If you are working in your own shadow, the lights are too high. This is why sconces, one on either side of the mirror, are better for best lighting/visibility.

I have seen this and it doesnt cause any more glare than a fixture mounted to the side or one that extends over the mirror from the top. Any part of the fixture that faces the mirror (excluding that part butted right against the glass) has to be decent looking because you will see its reflection in the mirror.

Hi Elaine, 120 watts of incandescent light should be more than adequate at the mirror. Yes, you should consider LED bulbs. To my eyes the best currently available are coming from Philips & CREE. Be sure to choose a dimmable bulb so you can vary the light level.

After reading more on this forum, I now understand that moving the sink a couple inches in either direction requires moving the drain pipe, but not the vent pipe, as long as the drain pipe and vent pipe are no more than 30" apart and are at least 2.5" apart. The existing vanity is 46" wide with the sink on center -- I am assuming that the vent pipe is centered on the vanity / sink; i.e., 23" away from the adjoining wall, and that the vent pipe is at most 3" thick. So, I am thinking that if I extend the vanity to 56" wide and center a lighted mirror (42" or 36" wide) above the vanity; i.e., 28" away from the adjoining wall then this will allow enough space to circumvent the vent pipe, regardless of whether the sink is centered or offset. I think that I read somewhere to allow for a 4" hole for pulling wires for the electric mirror.