I definitely agree that showing a progress bar makes a slow operation feel faster, I've seen this work many times. I think I disagree about the constant speed

I definitely agree that showing a progress bar makes a slow operation feel faster, I've seen this work many times. I think I disagree about the constant speed vs stuttering progress bar example though - Progress bars which progress smoothly are great if they are accurate. But because sometimes a UI will show a fake progress bar smoothly filling that will empty after filling and fill again, I've been trained to become skeptical of them. I don't think I've ever seen a stuttery progress bar that was "fake" in that way.