Having worked over several years in the cable television and telecommunications industry, I have been primarily focused on what is known as "linear programming". That is operators provide video services to subscribers using a TV guide format and you get what programming content when the provider decides to offer it.
Though I have dabbled in numerous Internet on-demand offerings, Boxee (http://www.boxee.tv/) appears to be the most promising offering of emerging technologies to enter the market. Boxee aggregates all of the existing online IPTV web portals and makes them available in one user-friendly interface for Apple (Mac), Linux and now Windows. It provides everything from Pod Casts, to YouTube, CNN to full length HD feature movies. Quite impressive!
Though currently only available for Alpha testers, I highly recommend that you sign up for a test ride as this promises to be the next big thing and a chilling threat for linear video providers.