Bueno, lo que yo entendí del link :
http://pkg-kde.alioth.debian.org/experimental.html, es que para instalar KDE 4.0, debo activar los repositorios "experimental branch", y también "testing (Lenny) y Unstable, y eso fue lo que hice :
#instalar KDE 4.0
deb
http://ftp.us.debian.org/debian/ experimental main non-free contrib
deb-src
http://ftp.us.debian.org/debian/ experimental main non-free contrib
# Official Debian Sites
#### Testing ######
deb
http://http.us.debian.org/debian testing main contrib non-free
deb
http://ftp.debian.debian.org/debian testing main contrib non-free
#### Unstable #####
deb
http://ftp.us.debian.org/debian unstable main non-free contrib
deb
http://ftp.debian.org/debian unstable main contrib non-free
Pero, actualizé y algunos repositorios no se actualizaron :
# aptitude update
Err
http://ftp.debian.debian.org testing Release.gpg
No pude resolver 'ftp.debian.debian.org'
Ign
http://ftp.debian.debian.org testing Release
Ign
http://ftp.debian.debian.org testing/main Packages
Ign
http://ftp.debian.debian.org testing/contrib Packages
Ign
http://ftp.debian.debian.org testing/non-free Packages
Err
http://ftp.debian.debian.org testing/main Packages
No pude resolver 'ftp.debian.debian.org'
Err
http://ftp.debian.debian.org testing/contrib Packages
No pude resolver 'ftp.debian.debian.org'
Err
http://ftp.debian.debian.org testing/non-free Packages
No pude resolver 'ftp.debian.debian.org'
Des:1
http://ftp.us.debian.org unstable Release.gpg [189B]
Des:2
http://http.us.debian.org testing Release.gpg [189B]
Des:3
http://ftp.debian.org experimental Release.gpg [189B]
Obj
http://ftp.us.debian.org unstable Release
Obj
http://http.us.debian.org testing Release
Des:4
http://ftp.debian.org unstable Release.gpg [189B]
Des:5
http://ftp.debian.org experimental Release [84,9kB]
Obj
http://http.us.debian.org testing/main Packages/DiffIndex
Obj
http://http.us.debian.org testing/contrib Packages/DiffIndex
Obj
http://http.us.debian.org testing/non-free Packages/DiffIndex
Des:6
http://ftp.debian.org unstable Release [86,4kB]
Des:7
http://ftp.debian.org experimental/main Packages [222kB]
Obj
http://ftp.us.debian.org unstable/main Packages/DiffIndex
Obj
http://ftp.us.debian.org unstable/non-free Packages/DiffIndex
Obj
http://ftp.us.debian.org unstable/contrib Packages/DiffIndex
Des:8
http://ftp.debian.org experimental/non-free Packages [968B]
Des:9
http://ftp.debian.org experimental/contrib Packages [1867B]
Des:10
http://ftp.debian.org experimental/main Sources [44,3kB]
Des:11
http://ftp.debian.org experimental/non-free Sources [652B]
Des:12
http://ftp.debian.org experimental/contrib Sources [440B]
Ign
http://ftp.debian.org unstable/main Packages
Des:13
http://ftp.debian.org unstable/contrib Packages [85,5kB]
Des:14
http://ftp.debian.org unstable/non-free Packages [105kB]
Des:15
http://ftp.debian.org unstable/main Packages [6802kB]
Descargados 7434kB en 56m44s (2183B/s).
Leyendo lista de paquetes... Hecho
Revisaré de nuevo los repositorios a ver que me falta, o si no se conectó bien a los servidores.