One of the things that you have to do whenever you have a film that is based on a TV series is to convince people that this is more than simply an extra long episode and that the movie really is worth the trip to the theater. And I think that’s a bit of what they are trying to do with the big, shiny letters against the black background. It screams “This is an event! It will be bigger and more glamorous than the TV version! You must be there!”
But even if that is not enough to really make the movie seem different than the series, the poster still should be successful in getting the Sex and the City audience interested in the film, as it signals that the movie will have many of the things that made the show interesting. The glamor, the glitz, the fashion, the class, the fun. Missing is the friendship between the ladies, but that is harder to convey in a poster and I understand their choice to go for a more clean image that doesn’t hit on it. And since the film only opens in may it’s quite possible that we will get posters featuring the other main characters and highlighting their comradery later on.
I also like the combination of the bright pink with the black background. It fits with the shows aesthetic and it’s distinctive enough and loud enough to get attention. And, as a bonus, it looks good.
Overall I think it’s a fine poster for this particular movie, as long as they are not interested in reaching a much broader audience than they used to reach with the show.