MORE SPOILERS
The thing that they spent an entire season on a wedding that lasted (for the audience) five minutes or so is the thing that bothers me the most. The season wasn't very good, it felt really dragged out. Meanwhile, the finale was full of stories that could be used this season. That's why I liked the finale, but not the season. They saved all the good parts for one episode, and the season suffered for it.
Also, future Ted made it pretty clear he didn't regret meeting Tracy, so that's just absurd.
Also, yes Barney did have to split with Robin. With that being said, he didn't have to become old Barney again. That's why it's a fan service to change him back. Although it would be criticized anyway. If he stayed "new Barney", people would have continued to say how lame Barney became in the end. Now they say it was silly to change him back.
In short, I liked the finale, but really didn't like this season.