But as far as I can tell you don't need it.
First I just tried changing the DNS on my ATV to the one they said to on their website. But Netflix just kept crashing.
Then reading it it says:
IMPORTANT:
To activate the service, in addition to AppleTV you need setup at least one computer (iPad, iPod and iPhone can be used as well) with our DNS and click on the "Check Serivce" on our home page.
So I signed up for the trial (literally enter your email, and that's it, no payment details) and then downloaded their setup program. Set it to on, and checked service and said working. Then back on my ATV logged onto Netflix, and all the US content was there and wasn't crashing.
Then back on my Laptop, I turned off their program, and uninstalled it. So my Laptop has nothing on it. But my ATV still has the changed DNS address, and Netflix still works on US content, even without the edited DNS' on my Laptop.
And I don't get how they can stop people just using the DNS address they give? Guess I'll find out in a week. I've read up and it seems people on PS3/X360 who have simply changed the DNS have it all working and don't have to pay. It only affects PC use if you don't pay the subscription.
Then again I'm not to clued up on this whole DNS stuff.