All excellent answers. If you are an FHA buyer, the lender requires any power tower to be outside of a "fall-line" which means in the unlikely event the tower should fall it will not land on the subject property.
Whether or not there are health issues have been debated for decades as we are exposed to EMF's in many forms on a regular basis. The effect on value is greatly impacted.
I raised my sons in the Cambrian school district, we lived across the street from power lines and now they are having children of their own. When we sold that home we did take a little hit, however we had gained significant appreciation over the years we owned. And if given the opportunity I would still live in that house.
It is a personal decision which should be researched to your own satisfaction.