Spoilers -- When did you first figure out the secret?
If it was before the very end?
I figured it out about halfway through, at the anniversary dinner. I heard there was a twist, so I was trying to figure out what it was. At first, it appears that people are interacting with Willis, so I didn't think he was a ghost. However, at the dinner, I realized that she never actually looked at him, and that's when it started clicking.
Usual Suspects took me a little longer, maybe 75% of the way through.
Any other good twist films out there? I love those. I've seem Memento, the ghost movie with DeNiro and the little girl, The Others, etc.
The Ring was scary partly because of the twist near the end -- wasn't really over like we thought it was.