My biggest requirement was an all-natural mattress - I don't like the idea of sleeping with flame-retardants and petro-chemical foams :-P
These guys matched my request with 100% natural latex with wool, all wrapped up in hemp fabric. Even better - it is the most comfortable mattress I have ever slept on.
I now have the same for my sofabed. You know that little internal groan you just did when I mentioned sofabed? Send it packing - gone are the days when you have to sacrifice comfort for space, this one is as comfy as my real bed (my guests rave about it :-)