One of the things that impresses me most is how they've managed to build such convincing looking ball joints at the elbows, wrists, etc., on what is actually a costume with a person inside. Not to mention the incredible range of movement the suit allows...yet still forcing movements to be slightly stiff robotic. Nowadays this would probably all be done with CGI, sadly.
The only way the design could've been more perfect is if the face was actually a makeup prosthetic glued to the person's face, to allow for more facial expression. The only control the actor really had over the face was the movement of the mouth when speaking. The eyelids and eyebrows were controlled remotely.
There was also a flight attendant version that was built, but never made it to screen (perhaps meant for the sequence when Andrew goes out searching for others of his kind?):
I can't help but think how much fun it would be to have one of these suits...the only problem is that the actress is a tiny 5'4, so even if one of these props magically came into my possession, it wouldn't fit me anyways. ;-)
Another disappointing thing is that these things really weren't built to last beyond its intended purpose of being used for filming. In these photos, you can see that the rubbery material on the palms of the hands is already deteriorating quite a bit:
(Images found by "rotwang.")