***SPOILERS, DUH! I very rarely watch things when they are "on" but due to social media I knew I had no choice. I even had to shut down my phone three hours in advance to avoid any east coast people ruining it for me.
Now there are some out there who are belittling the relationship he had with his wife because he ended up back with Robin. That just isn't the case. He loved his wife completely and never looked back. SHE DIED. So his life is supposed to end!? Even his kids called out that the entire story was aimed at telling them why he might want to revisit the idea of he and Robin now that they were past the child having age and now that he had lost the love of his life.
As far as the Robin and Barney of it all, they careers didn't meld, they couldn't ever find a way to both be happy. Barney also needed a kid, specifically a daughter to really grow up. Their marriage was simply a stunted adolescence. They both loved each other but not in that, I would give up the world to support you kind of way. Look at the tough choices Lily and Marshall made in order to make it work. I was sad to see the divorce but it wasn't entirely unexpected.
Another criticism is the fact that Ted and Tracy had so much chemistry that the writers should have changed their course when they saw it, despite the ending having been decided. Now that is just silly. Ted and Tracy should have chemistry, they get married, they have kids they are happy. Stop trying to make one relationship be a statement on the other! You can love two people totally, in entirely different ways. Ted was true to his heart always. He made a commitment and saw it through, now it is time to make a new commitment. You can have chemistry with more than one person, you just make a choice to commit.