Okay, so it isn't quite a native solution, but there is now a workaround that allows you to watch Netflix and other Silverlight content on Linux.
Having done this myself this morning, I can confirm it works on Ubuntu 12.04.
So, here it is:
sudo add-apt-repository ppa:pipelight/stable
sudo apt-get update
sudo apt-get install pipelight-multi
Once you've agreed to everything and completed the installation run:
pipelight-plugin --enable silverlight
Then you should be all ready to go. Fire up your browser and enjoy. I would advise that you also install a user agent switcher on your browser to spoof the fact that you're not on Windows.