Comcast has finally announced the initial availability of its Extreme 105 Xfinity Internet service, which is currently available to 40 million homes in major markets such as Baltimore, Boston, Chicago, Denver, Indianapolis, Miami, Philadelphia, Portland, Salt Lake City, San Francisco, and Washington DC.

First introduced last May, the service delivers download speeds of up to 105Mb/s (10Mb/s upstream), which is a substantial boost over the company's previous 50Mb/s service. According to the company's figures, you can download an HD movie in five minutes and a standard-def TV show in 20 seconds.

That speed comes at a premium, of course, as pricing is currently set at $105 per month when customers add it to their "Triple Play" bundle (TV, phone and Internet). That's an introductory rate which expires in 12 months, and then you're looking at $130 a month on top of your cable and phone.

Although that probably sounds like a lot, it's far less than the $200 per month Comcast originally intended to charge when it first announced its 105Mb/s tier. It's also relatively competitive with Verizon's flagship FiOS offering of 150Mb/s download and 35Mb/s upload for about $200 per month.

Considering Extreme 105 Xfinity requires DOCSIS 3.0, you'll probably have to upgrade your modem unless you intend to lease one from Comcast. Also, despite its blistering speeds, the new tier still has a data cap of 250GB per month for residential accounts. Business accounts are unlimited but cost more.

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