My understanding is that you need Mini Display port to watch HD movie content although without it you will get standard definition.
What are you talking about. First of all HDMI, DVI, and regular displayport are HDCP compliant. And according to reports, blu ray playback doesn't work on it when they tried it on the led 24 in windows (OS X has no blu ray playback support) on the macbook pro which lead may mean it is not fully HDCP compliant.