I bought a Wii U in November. Here is what I think so far:
For some reason I only enjoy Wii U when there's someone else physically present in the room to play along with me. Smash Bros alone is worth the price of admission; CoD Black Ops II is a serviceable shooter with online play; Dungeons and Dragons: Tower of Doom is like Golden Axe with better graphics. In this regard it's a bit like a 2015 version of the Nintendo 64 with its multiplayer hits. However, playing alone bores me, and so far the Wii U offers nothing as revolutionary as Mario 64 or Zelda: Ocarina of Time.
I don't think making the Wii U tablet gamepad mandatory was a good idea. It ought to have been an optional peripheral, like Kinect on the XBOX One. Most games are perfectly playable without a big 'ol screen in the middle of the controller. The imposed nature of the tablet gamepad makes for some illogical situations. I play Smash Bros with Gamecube controllers 90% of the time, but the tablet controller turns on anyway. The only way I've surmised to turn it off is to walk up the hallway till it's out of range, turn it off, then bring it back to my room. In CoD there are some menus which will display on the television but not on the tablet controller for some reason. No explanation is provided for this, it's just an arbitrary rule and it's a bit inconvenient if I'm lying on my bed playing where I can't see the TV. I wanted to play Splatoon solely on the tablet gamepad, but it kept prompting me to “look at the TV” while my TV was turned off. The only thing Splatoon displays on the gamepad is a map. It'd be nice to have the freedom to use the tablet gamepad any way I want, but apparently not all developers share this sentiment.
The tablet is really helpful for multiplayer. Player one can have his or her own point of view on the TV while player two has a separate POV on the gamepad screen. I like this most of all in multiplayer CoD. For Smash Bros and D&D it's neat to play in bed or wander around the house while the other players use the TV. However, if Nintendo had offered a Wii U without the tablet at a lower price, I'd have probably just bought that instead.