I tried to return my iPad 16GB that I ordered from the online Apple Store at a retail store just last week and was told no. The item wasn’t even opened since I decided to hold off for a 64GB 3G. They said the stores are separate and e-mailed me a FedEx return label.
I was able to return my online un-upend pre order at the apple store on 4/5 the day it came in. But I think they were willing to do that because saturday 4/3 when mine hadn't arrived I walked in there and bought a 32gig from them.