We went through the same thing, trying to work out what to put in the study/spare room - we already have a queen size bed in the other spare bedroom. We were thinking about a sofa-bed, and when we went into one shop, the salesman asked how long we wanted them to stay for, which was an interesting way to think of it i.e. 1-2 nights, 1 week, etc.
As we have the kids and grandson come down every so often, and occasionally two couples, we ended up going with this set up from IKEA. The guests have said it's comfortable and can be used as a day bed (if I need a nap when I'm working hard), or pull out into a double. How is MrDenali with an allen key?
Products
www.ikea.com