So, to get this back on track, here is a summary of the issue an my findings tonight. These are similar to what I've seen for the past month and what many others are reporting. It's not isolated to specific ISPs nor is it related to temporary drops in speed or time of day. The problems on the ATV are consistent and will persist through an entire movie and are non-existent on other devices.
ATV example short: starts at 4800 kbps and 1080p but after 4 seconds rebuffers and drops to 375 kbps and 384x288. It will generally stay at this low res level with occasional short term bumps.
Chromecast example short: starts at 235 kbps and steadily ramps up to 1750 in about 10 seconds and then 4300 kbps and finally 5800 kbps in another 10 secs where it remains.
First gen Roku: using debugging reports playing 2.6mbps stream. For some reason my Roku does not show the embedded details on the example short but picture quality is similar to 720p on the Chromecast before it fully ramps to 5800kbps which is all I believe the old Roku was capable of. Picture quality remains consistent on the Roku.
So, in summary, the problem is isolated to the ATV and Netflix app. I switched to the "high" option per the netfilx rep I spoke to which had no effect on the ATV quality but other devices are running fine. All on the same network with the Chromecast being wifi and the ATV and Roku wired.