When I used to use Netflix on my PC the best solution I had available was to run Windows XP inside of a virtual machine using VirtualBox.
The VirtualBox documentation actually does a fairly good job of explaining how to install and configure Windows in a newly-created VM:
Once the Windows VM is installed and you have Silverlight set up, you can get a movie playing, full-screen the browser window, then use your Linux window manager to display it however you want--fullscreen, managed, or floating. I used to set up like this so that I could watch a movie while working on personal projects.
I know this isn't exactly an alternative to Silverlight, but it does give you the opportunity to use Netflix without leaving your Linux OS which was the main requirement for me since I really do need Linux to be productive. It also gives me an opportunity to isolate Windows from my primary OS and to snapshot the Windows virtual disk in a known-good, virus-free state; any time something gets messed up in that OS, all I do is simply revert back to that good state and all is well.