If you plan on using it for HD DVD or Blu-Ray disks in the future (which you should if you are going to put that kind of money into it) you might want to make sure it is HDCP compliant. Check this out....
especially this part...
HD DVD and Blu-ray Disc players allow content providers to set an Image Constraint Token (ICT) flag that will only output full-resolution digital signals using HDCP. If such a player is connected to a non-HDCP-enabled television set and the content is flagged, the player will output a downsampled 960x540p signal. Most high-definition television sets currently in use are not HDCP-capable, and this would initially negate some of the key benefits of HD DVD and Blu-ray for those consumers.
I don't think the apple is HDCP compliant... but I'm not sure about the other two. I would seriously look into this if you are going to drop that kind of cash on a screen...
Oh yeah, check this out too...
However, if you're heading out this weekend to drop US$3,000 on a TV, chances are high that it will support HDCP. The same can't be said of monitors, sadly. Apple's US$2999.99 30" display doesn't support HDCP, and only a handful of Dell's various options do. If you're in the market for a new display, you might want to wait until some units are shipping with HDCP support.
This was written in August 2005 though... so the info is not the most up to date.