I just read Acts 10, where Peter is told to eat unclean food and go to a Gentile's house. It raised an interesting question, and I'm going to play "Judaism's advocate" with you for a minute. This is the most reasonable Jewish objection I've heard to Christianity, from people like Jacob Neusner. It goes like this:
God's Spirit would not reveal truth to His followers contrary to the written Word He inspired. Yet the New Testament claims that parts of the Old Testament are no longer legit - most clearly the unclean foods (Leviticus 11:2, 47; Mark 7:15-19; Acts 10:14).
If the Spirit DID do this, what basis do we have for arguing today that God won't reveal to an individual something contrary to God's Word?
I've got my own answer, but we need some activity around here in the comments again, so I'm being provocative - have at it!