I have used GameOutfitters twice, for Dragoneye and Archfiends, and had very good experiences. I ordered early, though.
Regarding Archfiends, I checked the GameOutfitter.com web site often, and noted they posted warnings that WotC changed the allocation and that there would be 2 waves. They also froze pre-ordering for a while as a result, until they had a better idea of when the second wave was likely to arrive.
My archfiends pre-order shipped immediately on the street date, and, IIRC, I got it the next day.