If your DHCP server requires DHCP_HOSTNAME you can't specify this in the install program. You have to edit ifcfg-eth0 by hand after booting and waiting x minutes for DHCP to time out. You should be able to specify this in the install.
This would take an extra screen we'd rather not add. Specifying your hostname *should* do the right thing though; if not it's a bug with dhcpcd.
I am not running dhcpd. I am using pump to connect to an @Home DHCP server. Will specifying the hostname work for this?
You don't actually need a separate screen. The "Network Configuration" screen actually has the hostname already on it but it is greyed out if "Configure using DHCP" is selected. All you need to do is over-load it so that it sets DHCP_HOSTNAME if that option is selected. This is obviously not going to make it into the next release but I re-open it for consideration for the one after that.