WordStar came in various varieties with version 7 the last before it changed direction to WordStar 2000 (which, incidentally, was well before the year 2000). This put death knell on WordStar as its keystrokes were different to previous ones. Making a stupid and unpopular change like that ought to be a lesson for every software developer
When WordStar 2000 was released I recall that when at an exhibition having an argument with Seymour Rubinstein, CEO of MicroPro, WS's developer, about these stupid changes. I told him bluntly that I would not be upgrading from version 7 as I saw no reason why I should relearn all the hard-earned keystrokes for little advantage. The fact that WordStar 2000 failed, it seems that I was far from being alone with that view.
Incidentally, for those who are not familiar with WordStar, MicroPro or Seymour Rubinstein—Seymour Rubinstein was the inventor of the now infamous EULA—End User License Agreement! WordStar was close to the first program to have an EULA attached (from memory I think WordMaster (an earlier WP that predated WordStar), was actually first—someone correct me if I'm wrong).