Others have asked for this as well but it sure would be swell if there was a tool-tip during Trade that let you get a general idea of the relative value of items for trade. It would save a LOT of time spent randomly plugging in crap in hopes of maximizing a deal.
Thanks!
(oh, and a "what would it take for you to give me this?" option - as is used in Civ IV - would be swell too)