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curl-6 on 10 December 2013
The Wii U is an excellent console and well worth the money if you like Nintendo's games.
Of the series you mentioned, Mario Kart and Smash are due out next year, Kart quite early on, in Spring. (Northern Hemisphere Spring, that is)
The biggest reason to get one right now is the superb Super Mario 3D World.
As for trading your PS3, how often do you play it? Are there games on it you feel you won't be able to do without?
