The best way to use this scheduler is to start a calendar from scratch or keep a shared one for specific purposes. As is the case with importing contacts from Outlook into Gmail, bringing Outlook calendar entries into Google Calendar is a somewhat labor-intensive, multistep process.
There's no wizard yet (although one is in the works). You can, however, import from applications that support the iCal and CSV formats.
Those who use Gmail—and have lots of friends or colleagues who use it as well—will find Google Calendar a great addition, as will those who just want an online calendar that's easy to use and share. Expect full integration with Gmail to be an ongoing process.