"I like the 2 characters-per-kart thing, it looks like it will add some strategy to the game but will still retain the same "Mario Kart" feel. People are always complaining when Nintendo makes sequels with no new ideas, yet the same thing happens when they do innovate (cel-shading in Zelda, 1st person view in Metroid, water pack in Mario, etc.)."
That's probably because aside from Metroid, none of those changes are extremely innovative. Cel-shading is a graphics only change, the water pack is little more than a few extra powers, and character-switching in Mario Kart seems like a minor weapons dynamic edition.