For example, if you try adding getters and setters to a simple Rect class, it's so fast to do it with Copilot you might just add more getters/setters than you initially wanted. You type pub fn right() and it autocompletes left + width. That's convenient and not something traditional code completion can do.
I wouldn't say it's "mission critical" however. It's just faster than copy pasting or Googling.
The vulnerability highlighted in the article appears to only exist if you put code straight from Copilot into anything without checking it first. That sounds insane to me. It's just as untrusted input as some random guy on the Internet.
[1] https://www.virtualcuriosities.com/articles/4935/coding-with...