I don't care if you write in .doc (Word) or .wps (Works) or .docx (Word2007) or any other format out there. When submitting, put it into .rtf. Unless they say otherwise.
Well, you can please yourselves. I do, at any rate, no matter what program I've been using. The odds are 99% that the editor has Word on their computer, but why take the chance? No matter what program, they can open .rtf. Even if they don't HAVE a program, they have WordPad and it knows what to do with .rtf too.
This is probably me throwing back to the days when programs like Works, Word, WordPerfect, OpenOffice, were violently unable to communicate with each other. These days, it's less of a problem, I realize. Still, old habits die hard. I would be uncomfortable sending the file as anything but .rtf anymore.