Finished laughing yet? OpenOffice.org can "affect grades" negatively!? What kind of sick and twisted teacher is saying that!? If anything, OpenOffice.org affected mine positively.
No, I will not list the approximately 9000 reasons I'm not using Microsoft Office unless when forced to. Obviously, OpenOffice.org was one of the first things I installed on my Mac when I got it.
If, and only if, you happen to be a multinational corporation then maybe Microsoft Office might be a good choice. (I do work for a multinational corporation using Microsoft Office there, thank you very much.) In all other cases what people actually mean when they postulate it is "better" is that it is what they are used to and that they are too lazy to get used to anything else.
Just the fact that Microsoft have felt the need to commence smearing (something they have no doubt been doing for years against Apple) speaks volumes about how far OpenOffice.org has come. This consideration soothes my anger quite a lot.