This. I think the ending is probably the single biggest influence on votes and comments. And on word of mouth. WOM isn't much of a thing here, though it probably does happen. But it is about to get bigger with the new public lists and especially once they implement subscribing to lists. I could see that turning into the biggest way a story spreads and gets views after a while, aside from the "new" lists. If enough people jump on and curate quality lists, that could become more reliable than tags.
No matter how good a story is, if the ending leaves the reader flat, he's checked out before he gets to the place to click the stars or the comment box. Or if he gets there, he's more ambivalent about how good he remembers the story being. My latest story, the one with the crazy rate of votes and comments, had an ending that, if I do say so myself, is just killer.
But of course, an ending is only good if the story behind it is good. If you're going for a more 'literary' story, a good meaningful ending should help the engagement. For a simple stroker, ending with a bang will do it. Do the buildup, then make it happen, then just end it.
