It's different for each guy naturally, but for me personally, I would say that it doesn't particularly add much attractiveness to a person... However, depending on the person, it may not take any attractiveness away either. Some people can indeed pull it off and look good in it. The problem is that many people can't pull it off and end up looking a lot worse than how they did before.
BASICALLY, On the plus side, it can make you stand out from other people and can also give you the same kind of vibe a tattoo does. It can look good on certain people. On the bad side, most people look bad with it and it makes them stand out for all the wrong reasons.
They're fucking hideous, looks like snot in your nose.
I voted D.
It looks ugly and harsh.
On a very pretty face, it can create an interesting dissonance. on top of that, some people consider it cool.
It's a pretty bad idea for any girl who isn't at -least- an 8 if she's worried about looks.
I love septum piercings on girls! True, for some girls the look doesn't work, but generally speaking I think that a pretty girl can look better with a septum piercing, as it draws attention to her face. I think the same effect is achieved with a nostril piercing, but I prefer the symmetry of a septum piercing (if a girl has both nostrils and a septum piercing I would be very happy with her look!).
Some guys do and some guys don't. I wouldn't avoid doing anything with my physical appearance just because some people might not like how it looks, though. There's always someone that's not going to like something about your look, so it's better to just worry about yourself! I don't have one, but I think they look good. Someone is going to like it!