J. Allen wrote:
If I would have found out before the film, it would have ruined the surprise. Yeah, I had a very strong suspicion, but I had been avoiding all spoilers, and made it to the movie unspoiled. When Harrison says he's Khan, I had a little "ha ha!" moment. Sure, others new, but I had remained unspoiled and it was a satisfying moment for me.
You didn't realize the it was already Khan after hearing the 72 number of torpedoes (The exact same number of Augments in "Space Seed") line and seeing the man that was frozen in tube? It was extremely obvious by that point.
There was also Khan's "I'm better" at "everything" line the trailer.