Saw it yesterday evening. If you've seen the trailer you've practically seen the film. Like a trailer, there is hardly any plot; all is mood. Call it a full-length trailer, but with the length you get the full dose of jet lag and culture shock.
It all depends on whether you can believe that the two main characters can get into a relationship. On the one hand, Bill Murray is made to look old (merciless lighting). On the other, Scarlett Johansson not only looks young but naïve. Two things made me believe: the disorienting strangeness of Tokyo and their respective spouses, who abandon them for the length of the film (and, you might suspect, afterwards too).