I've had several 40 foot containers, and currently have one right now. I like how secure they are, how you have an instant storage area once it's delivered. They are kind of ugly, but with some paint, they look a lot better for very little money. Size is the limiting factor, you only have enough room for some shelves on the sides, or enough space to pull something small into it like a four wheeler or small tractor. They also get very hot in summer, so you need additional venting, which really doesn't do anything for the heat issue, but it does help with the condensation issue that comes from the heating and cooling that they go through.
I've never seen a Quonset hut that I would want to own. I can't imagine why anybody would actually pay money for one. Instead, look into those carport type metal buildings if you want something quick, easy and fairly cost effective that is bigger then a container, but will take longer to build.