Streaming over netflix is going to give people varying quality because of a lot of factors. Network speed and how reliable that speed is a big factor. Lots of people think they have fast internet, but the connection needs to maintain those speeds for as long as you're streaming the content from netflix (an hour or longer, usually). If it drops or hiccups, your stream immediately gets lowered to accommodate, and the quality will suffer.
And there's how the source was created, too. Knight Rider, probably wasn't mastered with netflix in mind. a more recent movie on the other hand, will probably look a lot better.
I just recently got Apple TV, and I love it. The video quality streamed over either my iPad or iPhone is excellent, so long as the source video is good enough to begin with. If the video is poor quality, it might look ok on a small 3.5 inch screen, but will look bad on a large 1080p display.