Unity is a "good" engine.
It's not Unreal 3-4 and it's not CryEngine 3, but it's very capable.
This isn't the kind of news where Nintendo fans would be excited in the same sense as the Fox engine or anything.
What makes it exciting OS that Nintendo is not only removing any and all barriers and excuses for developers that may have any trepidation about the console, but they are literally rolling out the red carpet for any and all developers to ensure the largest opportunity for game creators and game players to enjoy the wii u console.
This is a very hungry Nintendo.
Theyre after the championship here.
I am a wannabe game developer of my own, and I feel like adding my comment to this topic. Whilst I don't use Unity, I can firmly tell you that the choice of engine does not dictate the graphical quality or style of the game created with it. A game can be created with the best engine in the world and look absolutely horrid, while a game made with a 2D engine like Game Maker can look quite impressive. Great graphics are about using what you've got and using it well, not grabbing an engine that was used to make graphically impressive games and using that. Even then, a good-looking fun game is better than a great-looking boring game any day of the week.
While what Nintendo's doing - making it easier to port Unity games to the Wii U - is good and definitely should help to encourage interesting game development, they and Unity are not, to my knowledge, removing any and all barriers for developers. It still will probably take a load of time and cash to develop a game for the Wii U, as it will almost certainly require an additional development license (I can hardly imagine that it currently costs an additional $400-1500 for an Android license, but a Wii U license will be free, or even similarly priced).
Even then, it probably wouldn't be as simple as "purchase the license, register your Unity executable, drop your game onto your Wii U SD card, and boom! ~You're now developing on the Wii U!~", though I'm sure that a quick workflow like that would be greatly appreciated by developers, indie and otherwise.
Finally, even if you purchase that license or become a licensed developer and make a great game, there's no guarantee at all that it will actually make it to the Wii U eShop, and if it doesn't, that's it. There won't be any other way to distribute a Wii U game. So, that risk will remain for indie developers.