Seems to help if you don't use the squashfs version of the firmware :).
So far, so good, it's got a DHCP IP and telnet is up and running.
Only problem now is root without a password doesn't allow loging in.
All openwrt docs seem to say use 'root' and no password when connecting via telnet the first time. Telnet is the only service that is up and running bu the only way to get in was to use the serial port.
This is not convenient since it means I'd have to take apart the devices any time I want to build a new version. On the other hand, since the OS is running on the card, I guess I just need to configure the OS as I'd like it then clone the card?