Silks:
Obviously nobody knows anything yet. Its way to early. Personally, I wouldn't dream of preordering online, because I just don't like ordering online. But specially situations like this which preordering at your local stores will most likely get you some special bonuses.
As of right now, nobody knows when the system is coming out, or cost, or even what games will be available. To preorder now might make you have to pay more than you should for a preorder and not be able to preorder games to walk in and just pickup the package.
I expect by October well begin hearing about preorders and launch games, and perhaps even have store demos to try a few first party games. That is when I will preorder, and stick around the store and talk and hopefully create more hype and buzz for Nintendo's new system. I will have everything I can ready to defend the system and sway potential buyers, because I want this to succeed. (That way my purchase will have tons of support.)