Without the DRM parts, making e.g. NetFlix streaming unusable on Linux (until recently, when someone managed to get Wine to the point where it can run Microsoft's own SilverLight DRM properly).
Even without DRM, Moonlight never worked correctly. I don't care for Netflix, it is not available in my country anyway. But I do care about other sites, for example autosalontv.cz and it never worked with Moonlight.