According to a source, you can opt into the new Netflix Watch Instantly movie player. The source is The Official Netflix Blog, so it’s probably accurate. This brings Netflix’s movie player to OS X for the first time (without running Windows) by using Microsoft’s Silverlight.
If you’re a slider and you use both Mac and Windows machines, once you opt into the Silverlight experience, you’re locked into to it for both platforms. If you’re a Windows-only user, you may wonder why bother with opting in at all? Well, maybe you hate Internet Explorer and you’ve always wanted to watch Netflix in Firefox. This is your chance.
However, there is no opting out yet. If the experience sucks, you’re stuck. It’s a beta, so you know what that means. I’m using it now and have already been hit with some errors. Some movies that used to work don’t play Silverlight yet (mostly Starz offerings).