What's your box?
I'll show you mine, if you show me yours! :)
I use a couple of different sets. For me, I use either a Hakoya two-level box (in ume blossom motif) that I bought at Loft last fall. Very sturdy, and I use it at least three times a week. I also have a Floream set with a keep-warm rice thermos and side dishes (that look a lot like denture cups, frankly). I use this set for warm leftovers, like mapo dofu or curry, since my workplace doesn't have a microwave.
My husband has two sets as well- one is a standard two-level rectangle box from Muji; very spare, like him. He also has a keep-warm set from Muji, which I like, because the food is kept in a plastic cup that fits inside a metal holder to keep it warm. This is more convenient than my keep-warm bottle which is all metal. Because my husband's cup is plastic, I can put the leftovers in it the night before, and then microwave it right out of the fridge the following morning before packing it in the metal cup to keep warm. Since mine is all metal, leftovers have to be stored in a separate container, heated, then transferred to the keep-warm container. Inefficient, and makes more dirty dishes.