Let's see, we have "God has shown us his mercy" because Camping claimed that he wouldn't make us suffer until the world is completely destroyed on Oct. 21, "Claim that something invisible and unfalsifiable really did happen" because he claimed that God did come down and pass judgment on everyone, "Revised date in near future" since he claimed the actual rapture would happen on Oct 21 when the world is destroyed, I guess you could throw in "All part of God's plan," and I read some of his followers claiming that it was a reason to believe more strongly. Unfortunately, no bingo.
Christian apologetics is the art of rolling a dog turd in sugar and selling it as a donut.