These instructions are from this site, but I don’t trust sites to stick around.

1. Make sure Netflix is setup to prefer HTML5. This is in Your Account-> Playback settings.
2. I have the latest nss (has to be equal to or better than 3.17.1)
3. Need Google Chrome (you can PROBABLY do this on Firefox with a similar plugin)
4. Get the User-Agent Switcher.
5. Fill it in with:
   • Name: Netflix Linux
   • String: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/38.0.2114.2 Safari/537.36
   • Group: (is filled in automatically)
   • Append?: Select ‘Replace’
   • Flag: IE
6. Click on Permanent Spoof list and put netflix.com in the domain (and select the rule you just made from the drop-box). Then click the add button.
7. Go to Netflix and watch instant videos.
8. And it works! So linux is perfectly capable, but apparently it’s not supported. I guess I can understand not wanting to support the infinite versions of Linux, but why not Ubuntu or Fedora? Maybe it’s coming? That’d be great.

I’ll later check if if it works on Ubuntu, too, with with this method.