There is a specific technical issue prevalent in a lot of Wii U games that bothers me, that being framerate judder. Perhaps most 3rd party games suffer from it, and even The Wonderful 101 has it. Essentially, even when affected games run at a steady 30fps or 60fps, there is a bad tick every few frames, making the game stutter. Sonic Racing Transformed is particularly struck by it.
The fact that no Ubisoft titles are affected (including the most complex, like AC4), while Capcom's mere 3DS port of Monster Hunter is eaten alive by framerate judder, suggests there's a fundamental adjustment that must be done to a game's engine to avoid it. But it's frustrating that so many games on the system suffer from it.