IMHO using network console (d-i over ssh) is most useful when used in conjuction with preseeding the network configuration and the network console password - if you can configure this using local input+output, then why use network console at all ? (Answer: for cold and noisy server rooms for example...)

Using network-console and preseeding

How to create a CD or USB image that enables network-console

After creating a basic CD or USB image, you must edit syslinux.cfg and create a preseeding file to automatically enable network-console.

Howto build an netboot-initrd

As explained above, you need d-i from sid (rc2 won't work), so you need a sid build environment... so chroot (see Build A Chroot) into it and:

Be sure to enable network autoconfiguration in your preseed.cfg! Also include the following lines to set a passwd for the network console (login with installer@host):

Using the network console in the Amazon Elastic Computer Cloud

Since Wheezy (7.6.0) D-I supports logging in the console by SSH key instead of password (592550, LP:184108).

For troubleshooting, pass DEBIAN_FRONTEND=text for a simpler console output.

Preseed file to activate the network console

d-i anna/choose_modules string network-console
d-i preseed/early_command string anna-install network-console

d-i network-console/password-disabled boolean true
d-i network-console/authorized_keys_url string
# OR
d-i network-console/password password r00tme
d-i network-console/password-again password r00tme

d-i mirror/suite string squeeze
d-i mirror/udeb/suite string sid