Are awesome. I have a 3 in my living room on a 40" LCD, and a 2 upstairs on a 24" LED.
My favorite channels are Netflix, Pandora, and Mullet
I originally bought the 3 because we were using my xbox to watch Netflix, and never really played games on it. That fucker heats up a bit, so the Roku was a logical move to reduce energy costs, and to keep my xbox from frying over running Netflix instead of some badass game.
I bought a 2 when I got a second TV, thinking the 3 was overkill for what I needed, and it plays content just as well, but I prefer the interface/speed of the 3.