JohnnyDelRay said:
In my experience battery life for the game pad is around 2-4 hours (depending on the brightness you select) but if you put it back on the charger (it has a charging cradle it comes with so you don't even have to plug anything in) while you take breaks I tend to get upwards to 5 hours on medium brightness (plenty bright for a well lit room). It charges quick. Also, the cord they have for it is long and small so it isn't much of a problem to have it plugged in while you game.
You might also be interested in Wonderful 101, another game made by Platinum for the Wii U. It is another high energy brawler like Bayonetta. I really like it.
Extra controllers can be expensive, but for almost all multiplayer games all you are going to need is 3 remotes and maybe a nunchuk for each of them, you can get those fairly cheap. Nintendo sells the combo for $25 refurbished. I would just use the gamepad for everything else, it is a really good controller.
Honestly, the value of the Wii U depends on your other gaming platforms. The Wii U is the different option. PS4 and Xbox offer similar experiences, experiences you can also get on the PC for the most part, while the Wii U does its own thing. For the gaming enthusiast I would not suggest the Wii U be the only gaming device (unless Nintendo is really your thing), but it should certainly be the second. Get a PS4, Xbox One or PC. You only need one of those. Then get a Wii U.