I have Qwest DSL which is not fast enough to stream HD from netflix. works on non HD. My DL speed is about 450 it says it needs a least 500. Strange thing is I can watch the HD on my computer no problem.
This device also lets you view youtube Vudo and other services.
The selection of movies to DL on Netflix is quantity not quality.
Roku.. My girlfriend has had it for year+... loves it. Movies may be limited but there are thousands available and they keep adding. Not up on this, but I hear that windows 7 premium/ultimate, has something that eliminates these boxes. Might want to check it out.