*** Correction ***
I stand corrected. I'm now convinced that the problem is in fact the newest software update for Apple TV and here's why: In my previous posts above, I noted no performance deficiences during off-peak times and no difference in performance vs my PS3. However, I had mistakenly assumed my ATV had the latest software (I have auto-update selected in preferences). In double checking this afternoon, I was notified that an update was available. Thinking it might be another fix, I installed it only to discover it was version 6.0.2!
After the update I had a serious degradation in performance. Using the same movie and procedure, at 3:30 PM (off-peak), I got a high of 3000 Kbps ONCE for about 5 seconds - out of the whole 11 minute film! Most often it ran at less than 500 Kbps. At the same time I got a consistent 5800 Kbps from my PS3. Sorry for my misleading posts above. I should have checked my software version first!
Bottom line - If you haven't updated to 6.0.2 don't!
According to iClarified on 11/18/2013, Apple has seeded version 6.1 to developers, so perhaps they are aware of the problem.
Here's the link - http://www.iclarified.com/35875/apple-releases-apple-tv-61-beta-firmware-to-deve lopers