Comcast is now delivering ultra high-speed Internet service to more than 40 million homes around the U.S., the company announced today.

Dubbed Extreme 105, the offering provides customers with 105Mbps download speeds and up to 10Mbps upload speeds. The service is available in several major markets, including San Francisco, Seattle, Washington, D.C., and Philadelphia, the cable provider said. It plans to roll it out in other markets going forward.

Reports of Comcast's 105Mbps service cropped up on the Web last year when a forum user posted what was claimed to be a bill from the cable provider marketing the new offering. A company spokesman told CNET today that the company has been "quietly rolling this out for several months."

Comcast said that it will be offering Extreme 105 to new and existing customers for "an introductory rate of $105 per month for 12 months." The deal is available as part of the company's Triple Play bundle, which includes Internet, phone, and television service. The company spokesman said the cable provider will offer Extreme 105 as a standalone service for $199.95 per month. In addition, those who sign up for Extreme 105 will receive a wireless gateway for the home.

As one might expect, opting for Extreme 105 will deliver vastly improved download speeds. According to Comcast, a 4GB HD film will download in five minutes over Extreme 105, compared to 1 hour and 30 minutes over 6Mbps service. A music album containing 10 songs will take just three seconds to download on Extreme 105, the company said.

Customers living in the supported markets can sign up now.