I have a deep need for closure in the fiction I read and the TV shows I watch (and I suppose, in my life). I like happy endings, weddings and good conquering evil. I can accept sad endings, particularly if I'm warned that it's sad. What I can't handle is a lack of closure--the wondering about what will happen.
For example, after watching the movie Gone With The Wind, I was so upset at the ending (will Scarlett and Rhett end up together?!?!) that I dreamt all night about the movie and created my own happy ending (they did!!!).
I knew going into Veronica Mars that there probably wouldn't be a lot of closure--after all, the producers/writers were hoping for a fourth season. And I was right. Veronica and her love interest Logan didn't end up together--although they did share "a look" before the show ended. But you know what's wonderful about watching TV on DVD? Writers' interviews!!!
An interview with creator/writer Rob Thomas reveals that the writers intended to keep those two together and had they fully known that the episode would have been for sure the last one, it may have ended with more closure. That made me happy (and able to sleep). See, writers and authors, closure is a beautiful thing.