This reminded me of my (fairly recent) experience reading Perdidio Street Station, by China Miéville. I think China Miéville is a wonderful writer with a huge imagination and a real gift for description and characterization, but I hated the ending of that book.
A lot of folks stress the importance of the beginning of a book, creating a hook to draw the reader in. And it's quite true that if you don't draw the reader in, you won't have any readers! Established writers may be able to get away with slow starts, but “new” writers don't have the luxury of assuming a reader (especially an editor or an agent) will stick with a story that drags at the beginning. But even with that, the ending is every bit as important.
Reading a book is a bit like establishing a relationship with another person. You feel each other out and decide if you want to be friends (i.e., keep reading). When the book is over, if the ending satisfies you, you're still friends. Maybe you'll read the same book again, and maybe you won't, but you will probably have positive feelings for the author. On the other hand, if the ending lets you down, you are much less likely to give that author another chance, just like a bad break-up means you're less likely to want to see a former Significant Other. I feel that once the book is over, it's the ending you remember most. How did you feel when you finished it controls a lot of how you feel about the book.
Of course, endings are, like plots themselves, personal. What works for one person doesn't work for another. Obviously, the editor or Perdido Street Station liked the ending enough to buy the book. So now I'm deciding what part of the feedback about my book's ending do I agree with. I want something that works better than what I've got now, but not something that doesn't satisfy me as a reader as well as a writer. I have to like my own damn story!