It only prevents a very casual hacker from seeing it. And that's not even really a hacker. That's just someone nearby looking for free internet most likely. Anyone who wants to will be able to see it. I believe it's very easy to find it if you have the right tools.

For the added overhead (adding it manually) it's not worth the effort IMO. Just leave it on and make sure you use the best security (i.e. not WEP) your hardware/drivers can handle.