I spent some time looking at the NetFlix desktop app. It is very ill equipped to be controlled as a media player in LinuxMCE.
At the very least, an application needs to have some form of sending definite actions to the screen in response to actions performed by the user to an Orbiter, or that the system does automatically in response to things happening.
The NetFlix desktop app is nothing more than the NetFlix web page, with a working Silverlight ActiveX plugin running in a full screened Firefox, and as such does not have any semblence of even keyboard shortcuts, that can be done in predictable contexts that say, "move the cursor left, move the cursor right, move the cursor up, move down, select, back"
If you send anything resembling cursor controls to the netflix app, since it is a web browser, it simply moves the window around. This is useless.
Contrast this to NetFlix running as an embedded app on a TV, or running inside a Roku box, or on a PS3 (all of which LinuxMCE actively supports), then you have a control interface that maps well to Orbiter.