Small hardware changes. I've been watching some usage statistics, and there's features operators in the field aren't using, mostly because they're too inconvenient.
(Funny story, last month there was a guy taking his amateur radio license test and when he finished up, he and I were talking. Turns out, he initially got turned on to the hobby because of the SSTV easter egg in Portal.)
Until I played one of the Carmen games from 1995 with Lynn Thigpen, and I found a note left behind from one of her agents, I didn't realize that Carmen pays her people too Lol