A new image of the new creature - commonly referred to as "Endermen" - was released recently (enhanced here, for light levels). This image is much more up-close-and-personal than the first, giving us a good look at the new creatures. It would seem that wearing a pumpkin prevents the new mob from seeing you, although this is unconfirmed at present.
Additionally, Notch mentioned a possible name-change for the newly minted mob, "Farlander" being suggested and, apparently, already in heavy use.
and then a :enderman:
is it just me, or does that screenshot look kinda fake?
They edited it so it's brighter. The original is on the MC Wiki: http://www.minecraftwiki.net/wiki/File:EndermenReddit.png
On the other, Farlander has a nice ring to it.