Let me sum it up in this way. It was one of the least enjoyable films I have ever forced myself to sit through. There are films that are hard to watch because the subject matter is difficult (Schindler's List). There are films that are just fun and require no thought (Pacific Rim). Some movies are not very good, some are really good, but most have at least some entertainment value if nothing else. The Hobbit trilogy in general and the Battle of the Five Armies in particular had not one iota of entertainment value. It wasn't fun, it wasn't exciting, it wasn't thought-provoking. It was just bad. Even my wife who normally is more gracious about stuff like this even commented how bad it was. Making it worse, it was way too long.
All I kept thinking was: please let it be over. In the end I was rooting for Azog to just kill Thorin just to get it over with. The orcs winning the battle of the five armies and conquering Middle Earth would be a small price to pay to reach a swifter end to this cinematic disaster; an audio-visual assault on the senses, on film-making, on acting and on simple human decency.
The interminably long battle at the end seemed to be the result of locking a dozen teen-aged boys locked in a room with endless Mountain Dew and incorporating every hair-brained idea they had into the scene. "Dude you know what would be awesome?! If they fought on ice floes! Sweeeeettttt!". "No, no, how about trolls with catapults on their back?! One of them could be a self-propelled battering ram!" On and on and on. Every single event was dragged out well beyond what was necessary. The crazy scene where Thorin sees himself drowning in gold looked like a scene that got cut from the original Willie Wonka and the Chocolate Factory, missing only a whimsical song from the Oompa Loompa's.
Martin Freeman was the lone bright spot in the movie. Perhaps someone could redo the book adaptation into a single movie, keeping him as Bilbo and ditching the rest. Even Ian McKellen looked like Ian McKellen trying to act like what Gandalf is supposed to be like. There was none of the smile barely hidden behind the gruff exterior, it was just "Hey, we are paying you a ton of money, act Gandalfy or something!".
It is hard to imagine the same guy who brought to the screen such a wonderful adaptation of the Lord of the Rings could somehow botch at every turn what should have been a fairly simple tale to tell. It went wrong when the decision was made to make a small, simple novel into three full-length films. Some huffing self-appointed Tolkien experts defend the film for incorporating other Tolkien lore into the movie but it is supposed to be the Hobbit, not a mishmash of Tolkien writings and an overly large CGI budget. The book is a wonderful story that is mostly light action woven into a story about friendship. Tolkien could have spent a lot of time writing about the battle at the end but he instead has the main character get knocked out and miss a bunch of it. Peter Jackson seems to have completely missed that.
In summary, you are much better off watching the old animated version or even better than that, just read the book.