While time will tell if the 3DS will hit the heights of its predecessor, this has to be a pretty good head start: reports are that the initial launch shipment of 400,000 3DS systems have sold out in Japan. Most systems tend to be in short supply their first week on sale, but the 400K number is actually pretty high for a first push out into stores. While most observers noted the lack of mob scenes and a rabid crowds, apparently the bulk of sales went to preorderers; maybe we're seeing a new breed of early adopter who doesn't feel the need to line up at ungodly hours just to be the first, or maybe stores are just tired of dealing with long, smelly lines of people waiting to get their fancy new toys.
Dale North of Destructoid has already observed larger retailers getting additional systems from Nintendo, meaning it's possible that the company will make a real effort to keep up with demand. Or maybe everyone will be freaking out for a year about how impossible these things are to get. We'll have to see if the process repeats itself in North America next month. I know I've got mine reserved, even if I have to wait a day or so for it to come to my door.
Confirmed: Japan sold out, 400,000 3DS sold in one day [Destructoid]