I use the gamepad all the time ...
I honestly don't get people like this. Personally, it's my favorite controller for most games, easily. Half the time I don't even play on my TV anymore. In my one bedroom apartment, I can literally fire up the gamepad and play anywhere in the apartment. And after the update this summer, it'll start up even faster.
Then there's games like Pikmin 3, Zombi U, W101, Trine 2, Deus Ex: HR, and more that use it in the gameplay pretty well.
Hell, it's worth it just for the map in Zelda: WW HD. It seems trivial. I thought it was trivial. ... until I played it. Then it hit me how much easier it is when the map is displayed at all times. The controller literally probably saved me thousands of button presses that I didn't need to do. Every single time I looked at that screen, it saved me 2 button presses. Every time you're sailing and you want to check what square in the map you're in, that's two presses of the start button, gone. Every time you're in a dungeon and want to see the map, or the chests, or the door you're looking for, or just to see what direction you're facing, that's 2 button presses, minimum. Even better, you can actually see the cursor on the map move for your character in real time now, and navigate dungeons or sailing that way.
If the guy is that anti-gamepad, why did he even get a Wii U?
Off-TV does affect the gameplay. You know how people say things sometimes like, "I prefer to play older JRPGs on handhelds because of the grind." Well, not only can you make virtually ANY Wii U game play like a handheld with a giant screen, triggers and dual joysticks, but you can then switch back to TV if you want on a whim, over and over, at any time. It's both. That is huge.