Vessel, the much-awaited online video startup founded by ex Hulu executives Jason Kilar and Richard Tom, finally opened its service to the public today. It may take time to see if users are willing to pay to watch Web videos that are usually free, but the company says brands like Chevy, Corona Extra, Land Rover and Jaguar, as well as Unilever's Axe, Dove, Suave and St. Ives, have signed up as advertisers.