"Have you ever known a Calvinist who wasn't sure s/he was an elect?"
One who claims to be a Calvinist is only stating the system through which they organized the truths of the scriptures; one of which is salvation by grace through faith alone. Because they have received that salvation the scriptures say they are part of the elect, so to answer your question, no, I have not met a true Calvinist who was not a believer and they believed their salvation flowed from God's sovereign election.
Me either. That's why it becomes a meaningless point for me.
If it's good for them, then I have not problem. I wonder though what its effect would be if someone loves God, would it matter?
If you found out you were not an elect, would you still love Christ?
While for the brief while I have been a Calvinist, I've never known a Calvinist who wasn't sure s/he was an elect. That being said, there seems to be plenty of Christians today who aren't sure if 1) they are elected (denying their salvation); or 2) if God elects people at all (denying the scriptures). That is really the scary thought.