That killed off-tv play for me straight away. The one thing I thought it would be good for would be for gaming in the bedroom for example with the console in another room. Could barely get out of the living room and connectivity was lost. I was gutted. I bought the WiiU just before the summer and thought I could game in the garden with it but noooope.
If you've got kids and they're hogging the tv, then I suppose it is useful. But, there's just so many work arounds in this scenario that it's almost a non-issue. The fact that you can record tv these days is a plus, or you can watch something on a tablet or laptop, it almost solves the issue without the need for the WiiU pad.
It was good for Sonic Racing (especially the multiplayer) and it worked well for Need for Speed, but it was unplayable with something like Arkham City due to the fact that you really needed a bigger screen to navigate where you were going.