Last time I used ed was to change the network config of a Linux instance in an S/390 LPAR, mostly because I was the only one with any experience with it (an ed clone from back in my CP/M days). Not that I didn't have to scour 1999's Internet for a decent cheat sheet. The mainframe guys were impressed, but I only started breathing when the LPAR came back up and we were able to get a telnet connection.