Some of this has already been said but...ATI claims they are HDCP "ready", they just don't have the actual HDCP chips on the cards so, no, no HDCP on the X1900s at the moment, also no Apple monitors support this right now, look into a dell 2407FPW or 3007FPW for HDCP support, but again, these are likely worthless unless you have an HDCP card.
Keep in mind though also, I haven't seen any software players for this, I think they are out there because there are some Acer notbooks running XP that have HD DVD drives in them.
How about iTunes HD Movies for download to purchase and/or rent. Or a HD rental/purchase service through the Xbox 360 both would be nice as long as they weren't HDCP encrypted content.
BTW ATI got sued for claiming HDCP "ready"
http://www.reghardware.co.uk/2006/05/09/atisued_over_hdcpclaim/