You couldn't watch it live--but you can see it now!
One of the points emphasized during the iPhone 4 press conference was that "phones aren't perfect," and Apple has posted additional videos, referenced during the iPhone 4 event, showing what it calls "smartphone antenna performance." "See demonstrations of smartphone antenna performances," Apple explains. "Every smartphone has a cellular antenna. And nearly every smartphone can lose signal strength if you hold is a certain way. To demonstrate this, we tested iPhone 4 alongside other smartphones."