I received a pair of the Zoom NXTs yesterday. I haven't played in them yet but I can understand why there would be zero break-in period. The upper is structured but VERY flexible. While the Vapor NXT took me months of play to finally get the shoes fitting and flexing to where I felt comfortable, these seem like they are going to be the complete opposite.
The fit is plenty roomy. I dare even say too roomy in my normal US men's 9. While I like the out of the box fit in the width--no crushing/pinching--I have concerns that the upper will stretch out over time making the fit a bit too loose in width. Also, there's a bit more gap between my big toe and the front of the shoe than I like.
For those that like the detached tongue, I was mistaken in my early assessment based renderings. This a booty style tongue as well BUT the attachment point makes for easy on and off with these shoes. I'm going to play around with my custom insoles to change the fit before I give a more detailed evaluation.