For those that experienced depression first hand or close by this movie will somehow give some comfort and recognition. The odd and sometimes bizar behavior and ways of thinking of a depressed person, the constant strain on the people close by, they are portrayed in a very realistic way.
You could argue the acting isn't state of the art and that the characters aren't all that likeable. I would hardly consider my rating based on entertainment value. Maybe the movie has more educational value. I for one did not 'enjoy' the movie and that's okay: it isn't meant to be entertainment.
I consider this movie a must-watch for anyone that doesn't understand depression: this is exactly what depression looks like.