This is... kinda surprising?
In 2006 Wii and ps3 pre-orders were sold out almost immediately. I knew people that camped out to reserve both systems, and I camped out at Best Buy for a Wii on launch day. I think that was due to the launch hysteria surrounding the supply constrained ps2 in 2001, which lead to fears of short supply for subsequent console releases.
People don't seem as obsessed with pre-ordering consoles these days, and I think that's been the case since Nintendo started releasing so many DS variants, which made it seem like new hardware was constantly available for pre-order, and reserving day one wasn't as essential. 3DS pre-orders didn't sell out immediately like Wii/ps3, and did PSV pre-orders sell out at all?
I figured the Wii U would sell out its pre-orders eventually, given consoles are generally a bigger deal than handhelds, but I'm surprised it happened quite so quickly. I'm not surprised it didn't happen within 30 minutes of going on sale like Wii/ps3, however. I think those days are over.
I pre-ordered my black Wii U via BestBuy.com a few hours ago. I don't have a 3DS or PSV yet.