Yoox, that end of the episode really answered so much more than anything even in the books.
This thread has some potential spoilers in it, but it does an amazing job piecing together what we do know about the White Walkers and forming a very good picture of who/what/why they are. Usually this kind of stuff is pretty stupid and easy to ignore, but this guy builds a pretty awesome case that makes a ton of sense in the GoT world. It leaves a lot unanswered but it does paint a pretty interesting picture of the White Walkers specifically.
http://www.reddit.com/r/asoiaf/comme...thers_and_the/