Every part of a story's important. First we meet the hero, then he goes on an adventure, and then the adventure ends. Beginning, middle, and end. You cut out any of the three major parts of a story and you don't have a story anymore, so of course they're all important, but I think the ending is especially so. It's the last thing the reader reads. It's the lingering taste that's left once the story is over, and it can either be a sweet after taste, or it can be a dud. We've all read a story, or seen a movie that we loved in the beginning and in the middle, but just didn't care for the ending. That can kill a story, or it can take something that would have been great and turn it into something mediocre. A good ending can have the opposite effect. It can raise an other wise by the numbers story into something memorable.
That's where I am right now with my new book I'm writing. I'm at the edges of the ending, and I'm trying to paint a picture that will be worth looking at; trying to make it something that ties everything together and makes everything that came before it seem that much more important. It's a tough order, but it's one worth trying to make, because when you get it right, people notice, and that's the funnest part about it really, having people enjoy the thing you've made.