I got 2 cheap backpacking solar ovens on ebay because I wanted to see what the set-up was and the directions with them. I used one on the last Oklahoma group camp-out that we had in the Spring and found that it got really really hot... not what I expected at all.
There is an art and a science to using a solar oven in that unless you get a self-adjusting (very expensive) one, you will need to adjust the reflector about every 10-15 minutes. You can only use these at full efficacy from around 10AM to around 3PM. I have tried earlier and later and with the small backpacking stove, it just doesn't work well for me.
Protip: If you are cooking anything that calls for liquid, use 3/4ths to 1/2 of the liquid called for because cooking it in a ziploc bag, none of the liquid will cook off and you will end up with noodle soup instead of noodles.
I feel that this would work best with freeze-dried foods that just need hot water added to the packet. You can definitely get water hot with it and in not as much time as one would think. Basically besides the stove itself (which is just a piece of cardboard with a black cooking surface and a mylar reflecting surface), all you need is a flat place to put it in the sun. A log turned on its end will work just fine for this.
I do recommend that if you are going to get one, that you take it out a few times and give it a try with different foods and different times of day. It is better to learn lessons now when it doesn't matter if you ruin food than later when it may be the last thing you had to eat and you've made noodle paste.