Very true.
So, again, it seems that I understand why so few people take on solar energy for their homes (unless you're talking about solar water heating, which is a little more prevalent).
I'd say so few people are doing it because the only tool in most people's toolbox is their checkbook.
It's all in the timing. You need to know what solar energy is available in your area (sticking up a 100W panel does not mean you always get 100W). If you want to store energy in your personal storage device (batteries) or use the grid as your storage (you get a 'credit' when your excess energy gets put on the grid during daylight, which 'cancels' the cost you pay for electricity that you need at midnight). Then look at the cost of solar equipment. And look at the cost of electricity in your area. It also makes a lot of sense to try to minimize your electrical requirements, so that you're not paying for a system that's really bigger than you need. Do you really need three TVs running all day? Then, when you've gathered all this information, consider that solar equipment costs are continually dropping and electrical rates are continually rising. You can estimate the rate at which your electric costs rise and factor that in your payback period formula. You could wait a couple years so the price of the equipment would drop some more. You could setup a formula to see how much the equipment needs to drop in price before you're satisfied with the length of the payback period - something like "I'm not going solar until it can pay for itself in eight years".
Less traditional aspects - I'm not a big fan of govt subsidies, but there are federal and local tax credit programs for installed solar systems. I think the federal program is 30% of the cost of the installed system. There are also companies that will foot the bill to install a solar system on your house, then charge you for the electricity it generates - SolarCity Solar PPA: Solar Power Purchase Agreement lets homeowners install solar power and save money every month with lower electricity costs.
Lots of things to consider.
Keith