The iPhone was introduced at Macworld 2007 without one mystery app. Apple later revealed that mystery app only 9 days before the iPhone launch to be YouTube which propelled iPhone hype into orbit.
With 52 days to go, and the iPad rumor mill kicking into gear, the question of the day is, “what is the iPad’s mystery icon?”
Personally, I’m looking forward to iChat and Dashboard widgets on iPad.
Update: Felipe makes a good point in the comments. On June 18, 2007, 11 days before the iPhone launch, Apple also upgraded the display hardware from plastic to glass. Glass display parts are $16 today, while camera parts are roughly $10.