I think the concept is solid. I think "execution" includes multiple angles. Very little advertising, hence many will not understand what the thing is or what it can really do, hence no interest. Marketing the device as something that will bring back the so-called "hard-core" or "core" gamer- absolutely wrong. The "core" gamers want a machine with serious horsepower that will play AAA titles for years, not a system with last-gen specs. The Wii didn't sell to "core" gamers for this reason, rather it drew in a larger, more casual crowd that has since migrated to Tablets and Phones. Getting those folk's attention and setting the Wii U as a more high-tech, "home Tablet-and-Console" gaming device with much more memory expansion ability than a Tablet, plus tangible controls might have been a way to position it. But this is my hindsight bias. 

I think the WIi did sell to core games at least intially. Then as time passed and the whole thing became more and more outdated more people migrated to HDs or they simply just played the HDs more. IMHO. Wii U isnt different enough from what core gamers already have and thats another reason its not flying off the shelves. 

Well at least it's selling then the PS Vita has, for these past 2 weeks (2013: week of July 13 & July 20).

Based on my experience I does very much enhance menu navigation. Having your menus on the pad that's easily accessible at the touch of a screen rather than having the pause and interrupting the flow of the game. Imagine playing Zelda OOT and switching between boots and iron boots with the touch of the screen rather that constantly having to pause and switch. And that just the tip of the benefits of the pad. So concept isn't the problem. It's the lack of games. That falls under execution. Many Wii U owners, including myself, are very happy with he pad and would rather have it and a lower spec console than what will be available in the PS4 and X1.

thats not really nothing to be proud of considering Vita has been outselling it for the better part of the year. 

but wouldnt you still have to look away from the TV to actually see whay you were pressing. Not trying to be an ass, but how is that better than pausing the menu? I dont think the concept is a problem at least not a big one, but right now no one not even Ninty has really shown what it can do and until it does or until it gets games people really want then it will continue to have the numbers it has. I know when i played it I had to look away from the TV to know what I was pressing.

IMHO i think the WII U might end up alot like the 3DS in terms of concept. No one really cares too much about the 3d now, after some swore it would make games better. I bet most of the best games on WIi U will barely use the gamepad, just like how some of the best games on WIi used little motion function

Exectution to me. Concept is like the E3 2011 video presentation, and that excited me. Execution has been so bad, full of patchs here and there and record droughs, delays and bad release schedules.

Cause you know that and played it for a fact? ;)

Easily execution. With a year on the market by itself, it has not taken advantage of it because it has nothing exciting.