Often simple questions get a bunch of short duplicate answers right away, where the answer is essentially one line of code (like "how do I parse an integer from this string?"). In this case I would think that if I'm one of the users who provided such an answer, but my answer didn't come first, I ought to just delete it since it's basically noise.
On the other hand sometimes you're writing a pretty thoughtful answer, you've been working on it for five minutes or so, and that dreaded "Load new answers" bar pops up at the top of the screen. You click it and sure enough, an answer has appeared that says basically what you were going to say.
This is a less cut-and-dried situation, in my mind. Generally I'm inclined to post my answer anyway, as when two people present similar ideas some users may find the first person's way of presenting those ideas clearer, while others may favor the second person's.
Basically what I want to ask is, should I go ahead and post my answer when it's so similar to someone else's? Or do you think it's better to supplement an existing answer (e.g., with a comment) by adding one's own thoughts to it?
Obviously there is an ulterior motivation here as well: if I've spent five minutes carefully wording an answer and then the time comes to abandon it, that's basically five minutes wasted.