Fortunately there's not a lot to be said here.  McAfee is arguably the crappiest system security available and now it looks as though the one-time industry leader is following McAfee's lead by being included as "vaporware" for Comcast customers.  "Vaporware" is software that is pretty much useless.  Why do you think they're giving it away?  Norton has probably laid off tons of programmers and analysts to save money and struck a deal with Comcast to buy a blanket license for their customers.  I used to use Norton myself until they adopted the Microsoft approach of focusing development efforts on visual candy rather than making it run more efficiently.  Hence, crap.  Question:  If it's so good, why are they giving it away?

Will the Comcast free Norton offer protect your system?  Somewhat, but at a performance price.  My suggestion would be to say "no thanks" and pick up a copy of Kaspersky Internet Security.