1 It's usually a generation behind
When the Wii originally came out people couldn't help notice that it was:
a) released a few years after Sony and Microsoft
b) the graphics and performance wasn't up to the current generations standards
Now that the Wii U is out they are boasting about how is is slightly better than current generation ... slightly, why would someone buy something that is only a bit better and will be obsolete pretty soon, I mean lets face it the PS4 and Xbox 720 aren't going to be far off and when it does come out it will probably put the Wii U to shame.
2 They have no clue how to prevent minors buying 18's
Okay imagine this, you go on psn, or xbox market, and you wish to buy an 18, simple is it not?, purchase it, it will check to see if your age appropriate then allow the transaction, Nintendo on the other hand have no clue, sure you can prove you're over 18 but it will still deny you, so what do you need to do to buy an 18 online? (even though you clearly are), any ideas?, no?, well then you do purchase it but it will only grant you access between 11pm and 3am, anyone who can't purchase an 18 at those time on Ninendo's shop, well you just can't get it then I'm afraid.
3 The controller isn't impressive as you might think
Sure it does seem pretty cool but let's consider a few things first of all, an Iphone is multi-touch functional whereas this controller only allows single touch (behind again it seems), it has an inwards facing camera to allow you to be put into the game, but most phones now have both camera's outside and inwards, if the controller had an outwards facing camera to track screen position for alignment with the TV screen well that would have been pretty decent.
4 Games are questionable
Nintendo is pretty obvious now for game releases they will always release Mario Bros, Mario Kart, Zelda, not that it's a bad thing but it isn't surprising now is it rather than reacting like "Yes they're making a new Mario game I can't wait", now it's more like "Another Mario not surprised", other games that they are releasing have also been out for other consoles for months to even a year or so ... yeah, doesn't seem that great
5 Core gamers?
The Wii came out with how many games for core gamers?, not alot right, most was for children or non-gamers, it was more of a conversion to gaming console, and I don't know but seeing most of the first day release games I still think they are doing the exact same without realizing it, sure they did say this was also for core gamers now but those release games say otherwise (I'm aware of ZombiU but compare that to how many children like games)
6 Wii U is supposedly better yet misses functions
Okay for something that is more "advance" the PS and Xbox it's still missing basics putting it way back, PS2 could play DVDs and CD's, PS3 came along and added to it by giving BluRay too, The Wii couldn't even do DVD, the Wii U however, Oh wait ... they still haven't incorporated it, sure they may have Nintendo TVii but still come on PS2 had DVD functionality that was 2000, twelve years later and Nintendo still haven't done it.
7 Wii U pad is kinda obsolete
The PSVita has two cameras, multiple touch based (pad and screen), and can also be usable for the PS3, so Sony can do what the Wii U does but with more touch and cameras they'd do it better, sure it may be more expensive but it'd be better
8 How much !!!
You can buy a PS3 160GB for under £200, and a Xbox 360 4GB for about the same, Wii U is under £400 but only 8-32GB this would be okay if the Wii U was alot more technological advanced over it's competitors but it is not much more powerful that the others so the price seems way too high
9 Nintendo is losing it
Remember how crazy people went over the Wii, Ds and that, people went insane for them, what about the 3DS, wasn't that much craze was there, Nintendo suffered, couldn't shift then, and brought down the price by alot all within the first few month of release, why?, because it was merely seen as a gimmick, DS - 3DS, they share the same name, look the same, same games for some (ds had mario kart, 3ds made another one) and play the same, the difference is that one is in 3d, the Wii and Wii U, same name, console looks the same, same games (both will have Wii fit) oh no I feel another gimmick coming along.
Sure others may disagree but this is what I think of when I hear talk (not that much going around) about the Wii U