It is fairly obvious after having played Zombi U that the Wii U is a capable console. But is it more capable than current HD twins by a large margin? The answer is definitely no simply because nothing sticks out technically. Had the Wii U had the guts to produce something making good use of substantially beefier hardware (basically, more complex action on screen), it would have done so because it is an obvious contributor to the 'wow' factor. It would make no sense to abstain from that argument when you try to sell the console. Thus, you can reasonably defend the idea that the Wii U cannot significantly outpower the PS3 and the X360.
That's one fact regarding the Wii U, arguably not the most important one. The real deal is to know if the control scheme will keep you playing the thing. And I must say, in that regard, the answer is no. I don't really like how you must always twist your wrist to reach for the bottom of the touch screen of the pad with your thumb when managing your inventory in Zombi U. Using the pad like a periscope in scanning mode feels dull when lift up down and on the side, and somehow out of place too. Finally, there is the software announced on the console so far. While they are indeed games that look appealing in the line-up, they will also be available on other consoles for the majority.
Thus, does the Wii U feel exciting enough for its price? The answer is, to me, no. Exclusive games look nothing particular, the novelty aspects don't take the world by storm and there is tons of things we do not know like online pricing model, what's ahead after the launch window when it comes to games and such. Nintendo has much work to do.