Make sure the warranty is still good, and I would ask for free service for a year if the shop isn't already offering it. Try to get a spec sheet online somewhere for that model bike and make sure that the parts that are supposed to be on the bike are there.
I have been to a couple shops where I see older bikes that have been stripped of the nicer parts and replaced with low quality parts. This kind of thing may account for why no one has bought it yet.
You have more bargaining power when you're buying a bike that is a couple years old. If you don't like the gripshifter ask for rapidfire shifters, they should be willing to do this free of charge.
Good luck, hopefully you will get a good deal and a sweet ride!!