We have Netflix and Hulu plus, and have a couple of Roku's for our TV's. I would get a Roku 3 over their older products.
We cut our cable back to the local channels that you get free with internet, so we pretty much just watch Netflix and Hulu. Hulu has commercials. We have it mainly for recent shows like The Colbert Report and The Daily Show. If you are still getting TV shows from another source, I would recommend Netflix or Amazon over Hulu.
Netflix and Amazon have a lot of good content, but it is generally older. If you want recent episodes of shows, Hulu plus is better, but it has commercials.