rj, that is rght to a certain extent. formally it isn't a word, while informally, long usage has given it a marginal sense of legitimacy. it does mark the writer as a bit sloppy, like using made-up words like 'copacetic'.
it's kind of like common misspellings. the reason to not use it is not that you won't be understood, but that knowledgeable readers will be distracted from your message for just a moment. kind of like a pump fake distracts a safety or linebacker just the moment needed to get him out of position. when you want to be understood by the educated reader as well as the bumpkin, use the safer choice. that way you hit both and your wording doesn't distract either from what you want to convey.
just my too sents.