I always laugh when someone calls a film slow. Unless I happen to know they've watched films by Tarkovsky or Angelopoulos, they really have no concept of a slow film. Sure, there are slower paced ones that those as well; but that would just be hyperbole.
The artistic licence does often bleed into indulgence though. Take the beginning of Coppola's Somewhere. I actually really like the film but it tries so very, very hard to make you stop watching. I just don't feel it's needed. The beauty of film is that we can say so much with so little, yet for some reason excess is seen as class and distinction.
I find it far more impressive when a director encapsulates a world in a moment. Take the first few shots of Super 8 for example. The classic film school response to me saying things like this is, "You just don't appreciate the art." No. Fuck off. The opening of Touch of Evil is art. The whole of Tarkovsky's Nostalghia is art.
A film shouldn't be praised just because it dares to be slow paced in the modern film scene. It should be praised if this pace served something greater.