Hi,
My sister uses her's nearly every day, and it's important to know a few things:
1. You need to tend to it all day, moving it with the sun.
2. Soak beans for 2 days before attempting to cook them. They will cook fast, and you will get more protein out of them.
3. Have fun with a solar cooker. My son and I built one last year, and we cooked all types of foods in it. We haven't bought the fancy type, because we don't have the money yet, but when we do, we will buy the Sun Oven.
http://www.sunoven.com/usa.asp
It's used all over the world, in India, South America, Israel, ect ect ect. The reason it is so important around the world is that people can't find adequete wood to burn anymore, to start a cook fire hot enough to cook food.
But the Sun Oven (or any good solar oven) will cook without wood, or gas, or electricity.
Good luck!