The Nexus is a very artifical way to "bring the generations" (ie, Kirk and Picard) together. Personally, I'd have prefered it if the Kirk and Picard strains of the plot had remained almost entirely seperate, but linked only in that they are each maybe facing the same problem 78 years apart. But then I also think people might have been disappointed with a movie that has Kirk and Picard in it, but doesn't actually see them interact with each other directly on screen. Unless somewhere near the end of the movie the ability for them to contact each other through time was established? Then again, it still wouldn't be seeing the two guys 'together' on-screen, would it, if their contact was limited to being over the view-screen.