Warning: Wall of text.
I'm not sure if anyone keeps up on non-gaming news, but a good chunk, if not most of you, have probably seen the biggest battle currently going on across consumer device makers: The fight to be THE set-top box.
Apple has the AppleTV, Google has GoogleTV, and now the Nexus Q. Microsoft is trying to turn their Xbox platform into the place to go for everything, from Netflix to Battlefield. Even Sony has done a pretty good job of trying to link all of their "Bravia" devices, including the PS3, together under a single ecosystem.
The average consumer has a tendency to not be a big fan of switching inputs on their television, and this is probably the largest contributor to everyone fighting so hard to stay on the TV. If you watch all of your movies on the Xbox, why bother switching over to the PS3 to start playing games? Vice versa, of course, and with digital distribution of games becoming far more prevalent in this generation (and probably ubiquitous in the next), game makers are doing everything possible to become the given choice.
So it's with this that it seems that the Wii U has pretty solid potential in terms of getting a non-trivial foothold here. Any one of us with a modern smartphone (iOS, Android, and even Windows) knows full well the power of notifications. Things that you wouldn't even bother with before, like social networking, becomes a lot easier when you have that simple buzz or "ping" signifying that something at least slightly relevant to your interests has come up.
The thing is that the Wii U gamepad, assuming Nintendo does this right (I think we all have more than simply "our doubts" here), has the potential to do this in the living room. The thing is, even when the system's not showing up on the TV, the pad is still there to handle both gaming AND all that Miiverse stuff. The latter is where the magic lies. You can get a notification for a game invite when you're watching a movie on the same game system whether it's the PS3 or the Xbox. However, you won't get ANY of that when you're on another system, or just on the Blu-Ray player, or just watching cable. The Wii U is pretty much going to be the ONLY system that can notify you about friends wanting to start a match in Mario Kart or have their town visited in Animal Crossing while you're using the TV for something else ENTIRELY. Even Smart Glass won't have that. Being an app on an iPad or a Droid means that it has to be run, and isn't going to be there at all times.
Keep in mind, this working correctly will depend on a LOT more competency in this sector than Nintendo has ever shown, so like I said, I have my doubts. But keeping people playing even when their TV is being used for something else may end up being the best long-term decision Nintendo's made on this system.
It's the only thing plugged into your TV that doesn't HAVE to try to do everything in order to stay relevant. All it has to do is play games, and that's an advantage that nobody else will have in this upcoming generation.
Well, at least until E3 2015 when everyone has a touchscreen controller.