They are only shipping 1 million 3DS's to the US for the realese. Last week I was at GameStop (Got Okami, Pokemon White and The Collector's Strategy Guide!) The clerk told me that it would be wise to pre-order since there will only be 1 million coming to the US.
They cost $249.99, but if you trade in your DSi XL, you only pay $149.99. With yourr DSi you pay, $179.99, and with your DS lite, you pay $199.99!
(Since I have 2 DS lites, and a DSi I would be able to pay only... Less than $100.00?)
I hope that you found this useful in choosing if you were going to pre-order or not!