I won't buy from MacMall. They are very rigid about returns. I bought a MBP a week before they were refreshed and MacMall refused to do anything for me. Had I bought anywhere else I could have either returned it for the newer one or gotten a rebate.
When I told them I wasn't going to do business with them one of the salespersons led me along saying she would do something to make up for it, and then just dropped the ball and ignored my further emails. I also had to pester them for my rebates.
Also, check
http://www.resellerratings.com/store/MacMall (a reliable ratings site). The rating for MacMall sucks at 2.88/10
Contrast that to Amazon. Last week I bought a Garmin GPS. Today it was $55 cheaper. They refunded the difference to me within an hour of asking.