I do not see the appeal in this.
First off the new PS Vita is this controller, except it looks nicer and has more features. (The Vita that is)
Next, you need to buy a whole new console, to play just a bit better games, the same thing you can get on PS3 or XBOX.
So really this was a total waste for Nintendo, and this is one thing I do not, and will not, enjoy.
If you ignore all features, the Wii U will still have more processing power than the Wii. So it is still important to get the new console. This might be similar to what the Vita will offer, but the important part is how it's used.
An example would be the iPad compared any other tablet. Even though they are both tablets, Apple seems to have found a better interface (or they have a very good PR team which is very possible.)