At this moment the only phone I would trade for my prized iPhone is the amazingly cool concept Window Phone from designer Seunghan Song. The phone would essentially be translucent, displaying information and images on a window-like surface in a form factor relatively similar to the iPhone's.
The killer feature of this concept phone is its ability to change the look of the display glass to match the current weather conditions of your location (i.e. sunny day equals clear screen, rainy day equals virtual droplets on your screen). The weather screen functions would also be interactive, allowing you to draw a message during a snowy and have it instantly transformed into an SMS message. Of course there are some impractical aspects of such a design, but with the newfound success of smartphones it's clear that some iteration of this kind of concept phone will likely see reality in the relatively near future.