I have Amazon Prime, Netflix, and Hulu Plus.
Hulu - great for current TV
Netflix - great for older TV seasons and movies
Amazon - HBO, newer movie releases plus rentals/downloads.
For example, I can only watch Avengers on Netflix - no Cap America or Iron Man but I can get those on Amazon. Amazon has a lot of subscriber and rental movies. We do take advantage of the 2 day shipping plus I use my Citi thank you points on Amazon to shop.
Amazon IV down side is the reliance on wifi which limits us when we're on the road.
Between the 3 yearly we still pay much less than a cable bundle and I don't run out of things to watch. We stream via TiVo, iPad, and iPhone.