A new AppleTV unit ($69) and three months of HBO ($30 - $15/mo with 1st month free) will still be under the average monthly cable bill. People holding onto cable primarily for HBO might very well consider that to be a good deal.
And buying a dedicated TV internet box is for people who can't figure out how to hook a computer to their entertainment system or don't realize its a much better way to go about it.
Been watching internet TV for several years with a computer I built that now holds multiple 2TB HDs All of it backed up with HD movies and HD Tv shows, Home Movies, photos etc. plus it can stream most of what the dedicated settop boxes can do AND I can record anything I stream just like a DVR.
Other than boxing they put on once every blue moon, I almost never watch HBO. They are about worthless.
I have all the premium movie channels and watch very little of it.