Not much coherence at this point, since that was probably the most emotionally draining hour of television I have ever watched. Hooooolllllyyyyyy crap.
1) Jared Padalecki freaking knocked it out of the park. I mean, damn! I have to admit, part of me has been hoping Sam would say yes just so we'd get to see Lucifer!Sam again, and I was not disappointed. Those scenes with the mirrors..."Are we having fun yet?"...*shudder*
2) Hurray for free will winning out in the end! Not only ITO Sam saying yes for a reason totally other than it was his Destiny (Luci's Luke Skywalker line was great), but when Michael tried to force him into it, you could tell from Sam's face when he was looking at Dean that because Dean had said no to Michael, Sam could do it, too.
3) Hurray for family including the Impala! That was such a nice way to structure the ep, including the Detroit bit at the beginning, and Sam's flashbacks about the car and Dean were so wonderful. Okay, so it was a bit of a cliched plot device to have evil averted at the last minute by a childhood memory, but it worked for me.
4) Raise your hand if you burst into tears when Dean said, "I'm not going to let him die alone." I came thiiiiiis close.
5) I'm not sure what to think about the Chuck-as-God thing. On the one hand, of course, the writer is God (hearkening back to one of my favorite X-Files eps), and that was a fine way to wrap up the storyline (honestly, I wouldn't be too upset if that was the final episode ever; well, I would be upset that there were no new episodes, but it was a good, if clunky, way to say farewell). OTOH, I was with Dean in being pissed at Him for bringing back Cas and Bobby but not Sam; and then at the very end, I realized that He had to wait until Dean kept his promise and went to Lisa and Ben like he told Sam he would before He could bring Sam back. Because like Dean said at the beginning, he had to grow up some, and resisting every fiber of his being wanting to either kill himself or try to mess with Lucifer's cage was growing up. It's what Dean wanted Sam to do after he himself went to Hell, and so he had to do it here.
6) Finally, I'm so pleased in how it turned out that Dean as the righteous man who broke the first seal was the only one who could end it. Because if he hadn't shown up at the cemetery (and wasn't that an entrance with style?) to talk to Sam, it would have been the smackdown of the millennium instead of Sam using the rings. Most importantly, in the end, I'm glad that Dean didn't have to say yes to Michael, didn't have to do anything supernatural to or with himself, in order to win. Just by being himself--loyal and cocky and fierce and watching out for Sammy--he saved the world.