I wanted to comment on the 4 disc sets, the packaging is just horrendous. They stack they partially on top of each other and you slide them in these plastic things at the top & bottom corners. They are not stable or are too stable where they are stuck. By not stable I mean they can be and have been displaced during shipping, basically if it get loose your DVD gets marked or scratched. Or if you put them in snug it takes an effort to remove the disc.
This has happened to me twice for me now. I dont like scratched up DVDs and have become reluctant to order any more unless they use a better method to hold their DVDs in.
I think they usually include what was on the original DVD but if movies were a two disk set they won't include the material on the second disk (or on the other side of the disk -The Big Sleep included a earlier cut of the movie on the reverse). You can check a bunch of reviews here:
http://www.dvdtalk.com/reviews/list.php and seach "tcm"
They pretty much copy the disc image of the most recently released DVD, so any extras on that DVD are ported. If it was originally released double-sided, it will just be the side with the main movie.