I am the owner and senior technician at an IT Consulting firm so believe me when I say I know computers, networks, and technology.
This is definitely an issue with the hardware/software on the Apple TV.
We have a Cox 50/5 Mbps Cox SOHO business connection, Cisco DOCSIS 3.0 modem, a SonicWall TZ 210W firewall/router, and an HP ProCurve gigabit switch. In short, some of the best network equipment you can buy for a home-office/small business. The AppleTV is up to date, speed tests are perfect (actually getting higher than 50/5), the other computers are off at the time of testing, tried wireless and wired, swapped the sonicwall with a D-LINK DIR-655 router and a Cisco ASA 5505, tried a different cable modem, etc. THE WORKS.
The buffering issue with the new Apple TV and Netflix has consistently worsened and now pauses 5-15 seconds every 4-6 minutes. Fairly unusable.
I've been on hold with Apple tech support while typing this message. I'm hoping for a replacement unit that works but judging from some of the comments I've read I won't hold my breath.