Here's a few facts followed by some opinion.
A quick analysis shows:
180 watt solar panel cost $567 from one website
http://sunelec.com/
$567 here in Alabama buys 7560 kwh of electricity (0.075 per kwh)
180 watt solar panel produces 7560kwh in 42000 hours of good sunshine
Assuming 300 of 360 sunny days in a year and an average 10 hour day(probably a generous assumption here), payback point occurs after about 14 years. This does not take into account the time value of money or the opportunity cost of having this money tied up in solar cells instead of invested in a CD or stable bonds or something. I have seen incentives in other states to go this route, but Alabama doesn't seem to do that.
So for the solar cell idea......Wanna help the environment by using less grid electricity? great idea. Wanna save money? Not so great idea.
Of course if you pay 0.30 for a kwh of electricty the payback time drops down to 3.5-4 years and makes it a better deal.
I am about to replace a roof and would love the architectural shingles that have the solar cells built in but it just doesn't seem worth it in this part of the country.
There is at least one company using the DMD digital mirror devices to focus more of the light on the sensitive junctions of the solar cells. This should allow up to a 40% increase in efficiency, but the cost of manufacturing becomes more.
Just my 0.02....that's worth ~0.27 kwh around here.