I thought it worked as an episode. That suicide-bomb switch stuff was pretty intense. Had it ended right after that (at the hour mark) it would have been a great episode, but not a season finale. The extra half hour of stuff wasn't honestly that great. Walker getting killed wasn't a big thing. You knew he was going to die from the beginning. They never developed that character at all. Sure they spent an episode explaining that he loves his kid and calls the house every day, but he had about 20 minutes of screen time total in the season. Killing him wasn't a huge revelation.
I feel that the show played it safe in the finale and failed to take the risk that I expected it to.