As you know, I didn't love how Harry Potter ended. That said, I was quite satisfied with it. Does it matter whether Harry lived or died in the end? Not particularly, at least not to me. Does it matter that there were flaws or lapses in logic? Nope. It was an amazing story with amazing characters who did amazing things. Not being blown away by the final installment didn't ruin that for me. I don't regret reading it and I got what I wanted from the series. J.K. Rowling could have had Ron flip on a boombox, blast Alice Cooper's School's Out, and kill everybody, and I still would have been satisfied. It wouldn't have changed the fact that for over 10 years, and for six+ books, I was riveted.
When Lost ended, I wrote about my feelings on satisfying endings. (There are no spoilers for those who want to go back and read it, but you'll notice that I do manage to talk about a certain epilogue.) In fact, another J.J. Abrams production is what got me thinking about endings in the first place. I was already playing around with whether endings really matter after seeing Harry, but then I saw Super 8.
I loved it. Like, loved it. It was basically every movie you've ever seen rolled into one, but somehow still managed to be fun and original. And the kids - the kids! They were just great. Anyway. When I went to express this love to my fellow geeks, I was met with shrugs and "yeah it was OK." Shocking! I didn't understand this "meh" attitude, especially from people whose opinions I respect on these matters.
Then I realized their problem. They had this desire to be satisfied. Like with Cloverfield, we don't really get to see the physical threat in Super 8 too often. For a monster movie, the danger is sort of beside the point. It's easy to compare that to Lost too. Pretty much all of J.J. Abrams' sci-fi works can be summed up with: "There's a monster. People are dealing with it. Focus on how they deal. Don't worry about that monster."
It's sort of infuriating when people say they "wasted six years" watching Lost. I feel bad for these types of people. Were they not still tuning it every week? Were they not coming up with theories and having fun and waiting to see what would happen next? How does one episode ruin that experience, as if it never mattered? If anyone was expecting logical answers in the end, then they missed what the show was really about - people reacting to crazy shit happening to them. Sure, the last episode was a bit of a cop-out, sort of confusing, and full of cliffhangers. That basically describes the entire series, so in my opinion, it was a pretty fitting ending.
But to many, it was unsatisfying and I suppose I understand that to an extent. For me, monsters are cool, but I'm way more interested in human nature, so in my opinion, storytellers like J.J. Abrams are perfect. Yes, I want the threat to be real and not metaphorical. Yes, I want to see some action. Yes, I need a plot to follow. But no, I don't need everything neatly wrapped up, or know where that monster came from, or even what it looks like. J.J. delivers on all of these points. (It's not like he's M. Night Shyamalan, who fails at plot, character, and endings.)
So, I ask again - do endings matter? Of course. As writers, you need to reach a conclusion that's in keeping with your story and that will satisfy your readers (there's a reason Ms. Rowling didn't just kill everybody). But, as readers, how much do they matter to you? Will an unsatisfying ending ruin an experience you otherwise enjoyed?
Oh, and see Super 8 if you haven't already. You'll want to hug it.