They keep the food really warm, hot and steamy, hot than the school dinners according to my children.
When I'm preparing the food, I fill the container with boiling water, which warms it through, then tip the water out just before I put the food in,
we often put jacket potatoes in the bottom and cold fillings in the top, and the child adds them together when they go to eat, they also have a plastic fork spoon,knife thing that they use, all works really well. soup and a sandwich is far nicer than just a cold lunch.
they are often on offer, so much cheaper, ours have paid for themselves over and over, just filled them with a beef stew to take to the beach. off in a min.
I use them on long car journeys very satisfying to have something wholesome instead of the garbage they offer at the services. They pay for themselves very quickly.