I got the Gamecube and Game Boy Advance on release day. I imported the DS from Canada long before the European release.
I had the Wii pre-ordered, but had to surrender that to my brother when I unexpectedly moved abroad for a couple of months.
Other than that, though, I've always had an "as soon as possible, depending on the games" attitude, and that's what I'm keeping for the upcoming consoles as well. I don't even have an Xbox 360 or a PlayStation 3 yet, since most of the games I'd want for them also have PC releases. I also don't have a 3DS yet, but that's mostly because it would be grossly irresponsible of me to purchase new hardware right now, but due to my crappy economy and my enormous backlog of cheaply purchased games.
But, yeah, I'll probably try to get the Wii U as soon as possible, and then I'll wait and see how things go with Sony and Microsoft's inevitable new consoles... as well as upgrading my PC, but that is unlikely to happen for at least another year or three.