You've had an AppleTV for decades? Nice. What did you watch in the early 90s? :-)

Oh, okay, you're exagurrating to make a point. I get that. And it's good, I do that at least fifty thousand times a day too.

You're right that Netflix offers a streaming-only account as of November 2010 and that it's cheaper than any of the DVD rental-in-the-mail options. As of this writing, it's only $7.99/month, which is a screaming good deal if you ask me!

You cannot, however, update or change your Netflix account from your AppleTV device or any other streaming device (Roku box, DVD play with built-in Netflix streaming, etc). Just not possible because that's not how they've built it.

Instead, you need to use a Web browser and log in to your Netflix account on their site, at which point it's fairly straightforward. When you're logged in, look on the top right and you'll see "Your Account & Help":

Click on it and on the right side of the screen, you'll see account options:

You'll want to choose "Change Plan", at which point you might well see what I then saw, but perhaps not:

Kinda fun being grandfathered in on an old account, but still, even for me a streaming only subscription to Netflix makes much more sense. I scroll down just a bit and see:

That's good. I check the radio box and scroll down to the bottom where there's the "Continue" option. A mouse click, and...

Yup, looks good to me. I click on "Confirm Change" and it reminds me that there are no physical DVDs included in the new Netflix streaming only plan:

Yeah, it's good, it's good. In fact, it is good, because I'm done:

That's how you change your Netflix account. As with any Web-based service, i find it useful to poke around in the settings and account configuration options on Netflix so I understand what's going on and how things are set up. You might find that beneficial too.