Do you use code completion and to what extent?

Back in the days of good old Delphi IDE I found some cool addon which had some very cool feature. It was using machine learning to detect some repetitive actions. Like when I get code:

  var poo = 
    [1,
     2,
     3,
     4];

and I start changing 1 to '1', 2 -> '2', then the addon all of sudden suggest me completion of other two cells.

It was amazing, too bad this feature did not come back in any of modern IDEs.

I love IntelliJ autocompletion while writing Java code, it increases my productivity so much that I can't imagine coding without it, however it could be better, always:)

We are planning to start work on implementing code-completion and intellisense but would like to get a feel for how useful the average dev finds this much revered IDE feature.

Do you have ideas for better ways it could be implemented beyond the current approach (which is really a holdover from an earlier era)?

Code completion is a godsend.