I recently borrowed a friend's Panasonic G1 and did a little comparison with the Olympus E-P1. Here's a video (taken with the SD880) of the test. Kit lenses were used on both cameras.
As you can see, the G1 focuses quicker and quieter than the Olympus. When switching lenses around (not shown in the video), the G1's 14-45 seems to focus a bit faster on the E-P1 than does the Oly's own collapsible 14-42. Likewise, the Oly lens on the Panny body also focuses faster, but not as fast as the Panny lens on the Panny body. Most of the speed of the G1's focusing does come from the body.