After having heard several points of view (thank y'all for sharing) here's my contribute to the discussion.
As Servy said
you should vote based on whether an answer is useful or not useful [...]
The definition of "useful" is left intentionally vague and open to interpretation.
So what's my definition? Josh Caswell said about it
I prefer to take a holistic interpretation of the "useful" criterion for answers, to wit, "Is this answer 'useful' in the context of the entire site?"
I do support the downvoting of answers when they don't constitute high-quality additions to our knowledge archive when considered as a whole
I'm with Josh on this.
I think just looking at how likely is the answer to help the OP is just part of the story and I typically take a broader context into consideration when voting.
Concerning the specific case, as I said in response to Lance Roberts
If you consider the topic with some domain knowledge about iOS and StackOverflow in general, it's not a helpful answer. If it has original content, it has a better fit as an answer to the original question; if it doesn't then it's not helpful as it provide much less information than the answers to the original question.
The point here is to help, and to help as much people as possible. As I said in the comments to the answer
This topic is sooo common, that a tremendous amount of people will come to StackOveflow looking for help. Scattering good pieces of information around several duplicate questions can maybe help the single OPs, but it's surely going to hurt future visitors.
To wrap it up,
Is the answer helpful to the OP?
Maybe. Or maybe a link to a much more complete answer (+143 votes) to the same question (+150 votes) would have been more beneficial.
Is the answer helpful to future visitors?
No. It's rephrasing information already present elsewhere on SO and, in case it adds any original content, it will probably never be found as much more popular questions on the subject exist.
Is the answer helpful to the iOS SO community?
No. It's been two months and we've been answering about the goddamn status bar every single day. It's quite enough.
Is the answer helpful to the SO community in general?
No. Seriously, we don't need people to think it's ok to post duplicate questions without putting some research effort before and neither we need people thinking that scattering information is helpful.
That being said, I took the decision of downvoting the answer, explaining my reasons to the author with a comment.