As he's already had a slight lack of story material, screenwriter Sam Catlin shouldn't have left out two of the six main actors, especially since Hank's political incorrectness may have helped to make things a bit more entertaining. However, he did, and therefore "Down" disappoints.
Walt's and Jesse's encounters in the episode were always very good, but sadly, these scenes were a minority group in an episode overcharged with unneeded insights into the family lives of the show's two protagonists and poorly written script. Some parts of that just aren't realistic and made me question the writer's intelligence while others were simply unnecessary. I highly dislike Jesse's parents (mostly because these two actors just aren't good) and unfortunately, this also merged with Aaron Paul giving a subpar performance. Bryan Cranston was the only really good actor in "Down" while Anna Gunn was over the top.
Now while it isn't a really bad episode just due to the show's general style being very good, I found myself bored while watching it, which is never a good attribute for anything that's made for the purpose of entertainment.