Kobato.tv has a little more information about the extras that come with Volume 1 of the limited edition DVD. The release date is January 29th.
DVD Volume 1 - limited edition extras
- CLAMP-illustrated box for the first 6 dvds
- mini-flash animation ('Kobato's Beginning')
- Kobato name tag
- Feature case, picture label, illustrated jacket*, 8-pg liner notes*
- gift application (for something when you buy the first 6 volumes)*
*also included with the regular DVD
Amazon.jp preorder link.