I don't normally come out of lurking, but the topic is kind of interesting to me since I can shed a little light on how the WiiU is doing, as a GS employee:
At my store, sales are... kind of weird, actually. It's not doing great, but it's far from doing badly. We had a line out the door Sunday morning so people could pick up their preorders and (usually) multiple games, and a lot of walk-ins begging for extra systems (which we didn't have due to preorder customers and wait-list customers getting first priority). Launch day, the demand was high for the first couple of hours. After that, though, there was a heck of a lot of, "Oh, what's the WiiU? Is that out?" It did not at ALL feel like the Wii launch, where EVERYONE knew the Wii had come out and EVERYBODY wanted one.
It's strange. We had a loooot of no-shows for preorders, and even after calling those customers to let them know we'd only hold their system for 48 hours we had almost no callbacks, which led to extras, which led to calling people on the waitlist, which led to some people freaking out and showing up to buy it right away and some people completely and totally losing interest and saying they didn't want one anymore.
The thing I hear the most from customers is, "I'm not going crazy over this/buying things/finding one, not this year," some especially saying, "Not after the first Wii." But the moment we have extras available, we've had some folks buying not just one, but sometimes more than one of the console at a time, and we still get people coming in and begging us to get more. I feel like people want it, and some are still out on "the hunt," but the majority seem so, so tired of the insanity of hunting and racing to get a system before it sells out/before Christmas.
Sales themselves? I can't give any numbers, but WiiU isn't hurting. People easily spend money on the system(s) and a handful of games and extra controllers. It just isn't selling out or as quickly as some might expect from previous console launches. People are tired of all the crazy. When it's in the store, though, it doesn't sit there for long waiting to be purchased.
*shrugs* So there you go.