Seems like a fair asking price but be prepared to go as low as $400 if necessary. I say this since the same model is available as a refurb for $449 with a one year warranty and new battery and shell direct from the Refurb store here. Of course that price does not include tax so the final price from apple would be closer to $480 or so.
I would also advertise when the warranty ends - like "Warrantied until June 15, 2013". Since the warranty is transferrable buys can rest knowing if there is a problem it can be resolved for free.