Overall, I enjoyed the movie. I loved Cumberbatch's Smaug, it was the perfect voice for the character. Luke Evans was also good as Bard the Bowman.
What is really bothering me though is that Jackson and Fran Walsh have morphed the book almost to the point of non-recognition. I was OK with the changes in AUJ, as I thought it didn't interfere with the overall fun nature of the story.
Having Kili have a love story with an elf that doesn't exist in the book and having him injured by a Morgul arrow, is just plain stupid.
By having this subplot with expanding the Necromancer story, they undermine the overall story and a fantastic villain in Smaug.
I feel this is a tale of two films. When the film is light on it's feet and acting as a child's adventure story, it soars. Whey they awkwardly try to connect it to the Rings trilogy it utterly fails. The story is about Bilbo's journey of courage, it's not about him getting tempted by the ring. They also undermine their own adaptation of the Rings trilogy as Gandalf already knows that Sauron has returned but somehow he forgets by the time TFOTR starts.
I'd love to give this film a 10/10, but the truth is, it doesn't deserve it. The best I could give it is 7.5/10, only for the performances and great effects.
There are also several unforgivable deviations from the book. When Smaug leaves Erabor to attack Lake town, Thorin and company could give a rats rear end, they are too obsessed with the plunder. The second is that Bilbo gets the Arkenstone and hides it from Thorin. Maybe this will be explored in the third, but they seem to totally bypass it. They also took out what could have been a funny lighthearted moment in how Gandalf introduces Thorin and company to Beorn.