I've been using the Roku 3 for the past couple of days and my initial impressions are very good. I've been hesitant about purchasing a Roku in the past because I've heard about their slow and clunky interface. But with the Roku 3 I found it to be as fast or faster than the Apple TV. It also has 700 official channels to choose from as well as 500 private channels. The new Roku also adds a headphone jack that allows you to privately listen to the TV without disturbing others in the room.
I'll post my full thoughts and details on the Roku 3 and their ecosystem after I've spent a little more time with it. Stay tuned.