Even though it was only two days before my first comprehensive exam, I had to watch the Lost finale. I'm a huge fan - it's the only show that I watch in real time (instead of just DVR). So, for the finale, we got together with some friends and made it into an event. We watched the two hour summary show before the finale, the 2.5 hour finale, and when I got home, I watch the hour of Jimmy Kimmel interviewing the cast.
Overall: So, in general, I really did like the finale. It was really sad, and also pretty final. It was character-based, which is what the producers said to expect, and seemed appropriate for the show. If they had chosen to answer all the random technical questions about the island, but not given closer to the characters, that would not have been as good. Everyone was pretty quiet when the show finally ended - definitely a sense of, "Wow... that's it. It's over."
Side Universe: I looooved the side universe. Ever since the Desmond episode this season, the parts of the show taking place in the side universe have been some of my favorite. It's so fun to see everyone find each other, and remember each other - such a cool idea!
What actually happened? Ok, it seems like people have different interpretations of exactly what happened in the show, so here's my take. I think they survived the plane crash, the island was real, and all of the adventure was real. Over the course of their adventure on the island, they all became very close and important to each other. The side universe was purgatory/limbo - and they all went there when they died (which wasn't all at the same time, hence Christian Shepard explaining that 'there's no time here'). In purgatory, they could take their time to find each other and remember everything that had happened to them, and once they had all remembered, then they could all "move on" together.
What about all the unanswered questions? It's true, there are a lot of things we still don't know. (Like who's dropping Dharma supplies on the island, still? And what was the deal with Walt? And why was Libby in the insane asylum in the flashbacks?) But like I said earlier, even if they had spent the finale explaining all these random things, it wouldn't have been very meaningful. Personally, I think they'll put out a book or a show or something that explains the Lost universe. Sort of like some of Tolkein's explanation of the Lord of the Rings world. I think they really do have answers for a lot of the questions that just didn't fit into the show, or weren't important enough to spend screen-time answering.
Awesome Videos: These are pretty much all thanks to Beth, but I'd recommend checking out the videos on this link - Particularly the ultimate list of unanswered questions, and the video showing the first and last 108 minutes of Lost. Incredible how similar they are.