They look very much like any other laptop. Especially the Acer and Samsung models, since the outside looks like other Acer and Samsung machines. The CR-48 is a little different, but not really enough so to be easily noticeable.
I don't have one, but I know a couple of people who bought them. I asked both of them a ton of questions and of course asked them to let me play with it. I know I could spot a Samsung Series 5 Chromebook in the wild, but I wouldn't be able to spot a cr-48 or Acer since I have no idea what they look like.