Here at Extremadura I've been using tbm's serial-console equipped nslu2 to improve Debian's nslu2 support. I've just uploaded version 0.10+r58-2 of nslu2-utils, which amoung other things supports generating usable initramfs images, and flashing the debian kernel and initramfs to the slug when the kernel package is upgraded.

Once integrated into debian-installer, this will improve the installation precedure described here, avoiding the need for the second upslug2 run.