First of all, the Wii U pad is a way more attractive option to pick up. I have it right next to my couch and I just grab it, sit down, turn on the tv, the console, and my cable box with the pad, and launch a game - I have Zombi U (loving it - 8/10 so far), Mario (best in the "New" series by far - 9/10 so far), Nintendo Land (i'll get to this, as it demonstrates why I am having a blast with it), Trine 2 (play this in bed at night), and Nano Assault Neo (addictive as hell, check it out everyone!).
Second, going between games, Miiverse, the amazingly fast internet browser (for a console), Netflix, and TV with one pad is so addicting, I'm hooked. I hardly ever put the pad down, which is odd, but it's already dominating my entertainment life. I don't need to be using the TV for certain things, so when my roommates want to play Halo 4, I simply play Mario, Trine 2, Nano Assault Neo, watch Netflix, browse the internet, or go on MiiVerse instead. The versatility of it is sucking me in more than anything.
Third, the asynchronous gameplay is absolutely brilliant. My brother came over to visit and we played Metroid Blast for hours. I was in Samus' ship, walking around the room while aiming by turning (works way better than the 3DS for some reason). This means that if I need to aim down, I'm looking at the floor. If I need to aim to the left, I turn to the left. My brother, on the other hand, has the entire main screen to himself. We're both having fun, but in completely separate realms doing completely different things. I honestly cannot wait for more ideas like this to come out. It's fun as shit and I wish Nintendo Land was a more complete game rather than a set of (admitently great) games.
Fourth, this thing has incredible diversity. ZombiU, the first real survivor horror experience I've had in a decade, scares the shit out of me. Mario is light hearted and fun. Nano Assault is videogame crack. Trine 2 is a great multiplayer adventure. And Nintendo Land is a party starter (don't get me started on the Mario Chase, Animal Crossing, or Luigi's Mansion games).
In sum, I've never had this much fun at launch.
[edit] The only thing that has sucked about my experience has been doing the first system update, and dealing with installing games. Even then, I just use the universal remote to watch TV for 20 minutes or so until it's done. :]