Do your research. Talk to the neighbors, the city building and health departments, check with the utility company and the EPA. Then make the choice that is right for you and your family.
The science on high voltage wires has shown no discernible evidence that there are health problems associated with these wires. Nevertheless, there are many people who do not believe the studies, and as Robert mentioned, find them unsightly, so what you need to know about buying a home with this issue is two-fold: 1) It will sell cheaper than its peers who do not have a similar issue 2) The buyer of this home will have to sell it cheaper than its peers in the future. So, it's not a bad idea, but know that you need to get it cheap, because you will have to sell it cheap. Be practical. If you like the house, and think you can stay there 10 years, and it fits your budget, than you need to consider it. Because the "same house" somewhere else will be more money. But if your time line is less than 5 years, I would get something "smaller" and "safer" that will be easier to sell in the future.