They would actually be very energy-efficent if buried to take advantage of the earth's natural heating/cooling effect
I've seen them used a lot in the oil patch for storage, as well as at a lot of companies for temporary storage. Hope your wife isn't into fashion and elegance.
Funny you should mention... it was her idea. The containers themselves are dirt cheap right now though, leaving plenty of money for renovation to make it look like a "real" house. Plus, if designed right, they're relatively immune to all types of natural disaster (including the straight-from-the-pages-of-the-worst-doomer-porn zombie hordes.)