Speculation about MacBook Pro battery life

There's lots of speculation about why Apple hasn't revealed expected battery life for the new MacBook Pro. The Apple site doesn't offer any specifics on battery life. The specs simply state that the MacBook Pro has a 60-watt-hour lithium-polymer battery (with integrated charge indicator LEDs), and include an unenlightening footnote that "battery life depends on configuration and use."

I asked a couple of Apple reps on the MacWorld showroom floor about the MacBook Pro's battery life, but didn't get very satisfying answers. One rep said battery life is currently unknown, but speculated that it should prove to be longer than in PowerBooks because the MacBook Pro's battery is larger (60-watt-hours as compared to 50-watt-hours in the latest 15 inch PowerBooks), the MacBook Pro has better power management features, and the Yona chip is more efficient in terms of power consumption. What do you make of Apple's silence about battery life?