The acting feels amateurish, but at least it's good amateur acting. And there is absolutely nothing new about the plot line. In fact, it's a very simple plot.
So the acting and story are mediocre... how could this be a good movie? I don't know, but it is. I think it's the writer-director combo. The sidebars and tangent scenes are interesting (even though they are awkward and random at times). It's successful in making the story feel real through the mundane mechanics, which makes the tempo changes that much better.
There's a lot of foreplay, I hope there's a sequel. If you like build up, this is 80% buildup.