Up to date Debian packages (*.deb) for libguestfs are now available:
http://libguestfs.org/download/binaries/debian-packages/
Please read the README file first.
Update
$ time guestfish -a /dev/null run : supported augeas yes inotify yes linuxfsuuid yes linuxmodules yes linuxxattrs yes luks yes lvm2 yes mknod yes ntfs3g yes ntfsprogs yes realpath yes scrub yes selinux yes xz yes zerofree yes real 0m17.335s user 0m16.061s sys 0m0.608s
Note that time is running Debian inside a virtual machine. On native hardware with KVM that command should run much more quickly.