Ah, no, sorry. It's more GUI because Plan9 terminals allow editing everything on screen. So I can type my text in ed and then use my mouse to position the cursor somewhere up, select text, and make a change.

Perhaps I should have phrased it differently, if all I cared about was ed commands I could have used Plan9's ed in conjunction with a plan9 terminal, like 9term.

In UNIX I use plan9port which has a port of ed, and 9term, a terminal that acts like a Plan9 terminal.