I bought both this and an Amazon stick. The Roku is sluggish and stuttery in menus, but video, including HD, plays without issues. The Amazon stick was smoother in the menus, but the video playback, even in SD, was jittery and glitchy. I recognize that tradeoffs need to be made for such a small form-factor, and I'm glad Roku made the right ones.
It is very laggy and the commands you hit are delayed or didn't work so you have to often keep hitting the button for it to work sometimes. But it's a good thing for extra tvs in Your house for which you don't want to buy the expensive New Roku.