There aren't really any "bad" main systems anymore. Even the Vita ... there's plenty to enjoy if you're open minded about it.
Wii U is a good system *if* you don't need a several new games every month and are fine with a smaller handful of good games per year, specifically if you like Nintendo IP.
Getting in now while the system has grown through most of its growing pains is a good time too, because you have several good games in the back catalog, several more available now for dirt cheap (ie: Zombi U, Rayman Legends are both $20 in my area) and you're in the midst of new games like Hyrule Warriors and Bayonetta 2 just around the corner.