Sales wise, the console has not been doing too well since release unfortunately - but this is largely down to Nintendo's marketing issue with the console and misconceptions clouding consumers perception of what exactly the Wii U is.
The Wii U is selling with some consistency, but the numbers are still fairly low.
Mario Kart 8 is turning heads and I think the console in general will continue to do so this year. Zelda U expected to be shown off at E3 in June, Smash 4 is coming at the end of year, Hyrule Warriors and Bayonetta 2 are expected sometime before end of year too.
The Wii U may not become a significant success in any form, but it will continue to stand out as a unique product more and more imo.
Even as someone who has always enjoyed Nintendo games, I was sceptical about picking up a Wii U when I did so last August,
but I'm so glad that I did!. Aside my PC it's my most played system since I got it, by a long mile, and I expect it will continue to be so well into next year at least.
The OS interface is easy to use with some nice little features and miiverse is cool.
eShop purchases are still tied to the console unfortunately, and it doesn't have anything like the XBL's party and voice chat systems(it's up to game devs to include voice chat in games atm), but it does have a friends system integrated with miiverse and using NNIDs(like gamertags i guess). In terms of online multiplayer there isn't much right now outside of Wii Sports Club, but Kart 8 will have 12 player online. I have been playing a bit of Tekken Tag 2 online recently and have not had any lag issues. I use netflix a lot on it too and it's solid.
3rd party support is very limited but can fill some gaps, there's not much but it's mostly high quality stuff - generally, multi-plat versions of games on Wii U are good. There's some good indie games available and there's the virtual console too... and backwards compat with all Wii games.
If you enjoy the more quirky Nintendo titles like Pikmin alongside Mario/Zelda/Kart,
or if you can relate to the image in the spoiler below, then I'd say without a doubt go for it!
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If you are still unsure, Mario kart 8 releases on May 30th and E3 takes place a couple of weeks after, so wait till around that time and the choice should be much easier - MS/Sony will have a lot to show off at E3 too.
