Your enjoyment of this movie completely depends on the mindset you have going into it. I have a friend who (for some reason, despite seeing the other two movies) expected it to be a faithful adaptation of the book, and he came away raging and swearing it was the worst movie he'd ever seen. I went in expecting a blockbuster action movie loosely based on the Hobbit and came away very impressed.
That said, there were a few parts I had issues with. Legolas' part, for example, was way overdone. I'm not against his inclusion in these movies, but some of the scenes in this particular one were over the top even by Peter Jackson standards. The bat-riding and running up the collapsing bridge are two in particular that come to mind.
Alfrid, the Master's bumbling second-in-command, had far too many appearances imo. Some of his scenes were welcome comic relief, but it got to the point where the setting would continuously switch from an intense battle sequence to Alfrid's shenanigans and I would groan. Plus, you know everything you're going to know about his character after the first two minutes of meeting him.
That said, I definitely enjoyed this movie and I'll probably end up seeing it a second time.
Yes, I began my journey alone, and I ended it alone.
But that does not mean that I walked alone. ~ Brandon Sanderson