I hate to disagree, but having read all 33 pages of the discussion to this point, we know this much:
- ISP does not matter. Low quality stream has happened on many different ISPs
- time of day might matter. Many purported solutions have been tried at non-peak hours, with quality problems resuming later
- no user-attempted solution has permanently solved the problem, including power cycling, resetting network settings, downgrading operating systems, changing Netflix settings, etc
But this is not just an ATV issue. I have 2 iPhone 4S', an iPad 2 and an iPad 4 and the only device with a problem is the ipad 4. Another user had a similar issue, with his ipad air showing poor quality and not his ipad 2.
It is definitely a Netflix app issue. It is definitely on Apple devices. But it is not just the ATV.
Finally, if you want a fix, do not just post here. Apple does not read forums looking for bugs. Netflix does not read this forum. You need to call/contact Apple or Netflix, a lot, if you want a fix.
Others have posted contact information already in this thread, but