I've had an open case about a strange component rattle in my my 4 month old rMBP (2.6/16/512), and after several trips to the genius bar and talking to a sr. advisor, I got an awesome genius who offered me a free in store replacement. I'm trying to time when the order is placed so that I will be in town when the replacement arrives. They told me in-store that I must pick up the new unit within two days of its arrival. Any experiences with these in-store swaps on custom ordered models? Does it only take 2-3 days for them to get the new computer in once the order is placed? Thanks!