Autocomplete is one thing. Getting a list of suggestions is more important, because you might not know the name of the function.

That's not a big argument, as a process doesn't have to be "the most" time consuming part of programming to have a big negative impact.

Annoying context switches and slowdowns to lookup function naming and possible options (without autocomplete) can still interfere with the flow of a programmer as he writes a program...

Knowing what you can and can't do with an object is the time consuming part. Once you know that answer, the writing is relatively insignificant.

To test that this argument doesn't work, consider introducing a 400 ms delay on your keystrokes. Writing will still be the least time consuming task. Then compare with code you write without the delay. I have a reasonable hypothesis how the test will turn out.