I have to agree with Steve's assessment. The extras and featurettes that ARE there are really good, and there are some great outtakes and behind the scenes shots, as well as the aforementioned (and posted) shots of the miniatures. I won my copy in a contest, so it was a freebie. For $40-$50 though, I would have been disappointed. There aren't a lot of featurettes, and some (if not all) of the commentary tracks included in a couple of episodes have already been included in other sets.
For what's included, and the packaging itself, I would expect this to be $20-$25. For the $50 retail price, I would have expected a lot more "vault" content. I won't say that I'm disappointed, because I loved the stuff that was there. I am somewhat surprised that there isn't more.