A bunch of Star Trek fans who showed up for a screening of Star Trek II: The Wrath Of Khan in Austin, Texas were cruelly tricked into watching the new J.J, Abrams-directed reboot instead. Or maybe it wasn't so cruel. Here's the scoop from trekmovie.com (which may not be the most unbiased source):

Tonight Paramount pulled off one of the coolest stunts in fan history. Promoted as just a 10 minute preview of the new Star Trek to show along with The Wrath of Khan, tonight fans in Austin, TX were actually shown the entire new Star Trek movie. The event included surprise guests, including the original Spock himself, Leonard Nimoy.

The reaction? Positive:

According to a friend who called in to TrekMovie after the event, the audience reaction was very positive. There were "genuine laughs" at the jokes and "quiet moments" with the serious character stuff. And apparently the crowd applauded at the introduction to each character. The film ended with a standing ovation.

The film leaves the hothouse environment of super-fandom May 8th. (May 7th if you live in Australia or New Zealand.)