I'm not sure how long it will be before we get all the sports I care about (pro and college football and basketball, and mlb baseball) streaming HD live at reasonable subscription prices, but I can't wait.
It seems like you could do a combination of subscription Hulu Plus, Netflix, and the eventual streaming sports options, and still come up well below what cable charges for HD digital service.
Maybe the "Al a Carte Cable" model that many consumers want will come in the form of some online service, or at least the threat of such a service forces the cable companies to rethink their strategies.
At least with downloaded (DRM-free) media, I will always be able to play the files I paid for. No such guarantees with cloud services.