I get the feeling NewJerseyJoe doesn’t realize that he got it backwards or a least is communicating his comment backwards.
Though non-Jews are forbidden from observing Jewish holidays in the way that Jews do (or from creating their own holidays), they are nevertheless to orient their lives around the Jewish calendar, and Shavu`ot is very apropos for them, as it was at Sinai that the Seven Noachide Laws were proclaimed in their final, eternal form.
Shavu`ot is also the most ignored of all the Jewish holidays. It has no external characteristic rituals as the others do (being instead a celebration of the source of all the mitzvot). Chanukkah, reinterpreted in a sort of ACLU fashion, has become the biggest holiday of the year while Shavu`ot is strenuously ignored.
Shavu`ot has two other strange characteristics: the event it celebrates is not explicitly connected to it in the Written Torah, and its maftir portion doesn't include a description of all the special offerings for the holiday (one is mentioned only in Leviticus 23).
There are only two kinds of religion in the world: the mythological and the historical. Of the latter, all but one were founded by people who claimed to have been authorized by G-d or to have (chas vechalilah!) been an avatar of G-d. Only one religion in all world history has a historical founding in which the invisible, unincarnated G-d spoke to an entire nation. Only one.
You can spin it all you want, but that says it all, my friends. That says it all.
Believing is one thing. But knowing--that's what it's about!