1. The "environmental damage" shading would cause would drive envirowhacks lividly crazier, with predictable results;
2. the massive transmission problems would be a nightmare;
3. the 'eggs in one basket' problem with any kind of disaster, would be catastrophic;
4. transmission losses by the time power reached the East Coast would be massive;
5. Great, while the sun was up...photovoltaics don't work at night, and are poor early & late in the day.
Build more nuke plants, where & as needed.
Article in Scientific American if you get a chance. I’m not endorsing this but it lays out whole solar scheme:
http://www.sciam.com/article.cfm?id=a-solar-grand-plan&page=1