I needed a new MBA week before last; decided that I really needed 8GB, so went to store. Although they said that for memory, "2GB was required, 4GB was standard, 8GB was recommended," only 4GB was available in the store. I asked if the 8GB was shipped from California, and the sales guy assured me that it would be. Somehow, he seemed to think that China was in California, but in any event, my new machine arrived exactly the day they predicted.
It replaced my second generation MBA, and is much faster, as near as I can tell. Well pleased.