Don't get suckered in by low prices for two years.
We did that, got a year of low priced cable access with terrible SD picture quality. Their user interface for on demand content was infuriatingly slow and byzantine, and when I tried to cancel the cable service but retain Internet, they continued to bill me for cable for months even after I returned the cable box.
I finally got so upset with their terrible customer service that I disputed the charges through Capital One, which finally got the attention of someone at Comcast and they resolved the issue.
Since then we've only used Comcast for Internet service and steam everything else through a Roku 3.
Between Netflix and Amazon prime there's almost always something on for free, or we can rent movies via Amazon for a few bucks.
About the only use cases where a roku isn't the best option is for people who are sports fans or news junkies.
Comcast sucks, and I strongly recommend against getting sucked in by promises of low introductory pricing. They more than make up for it later.