I agree there should be visual feedback, but maybe more of a compromise. E.g. bundle all unzip tasks into 1 single progress bar and rotate text strings for informing which task is underway.
If operation takes more than human's average reaction time, progress should be shown. Usually 250ms. Jef Raskin and others wrote a bookshelf about that a decade ago, but I still see strange solutions everywhere.
This is basically what happens in third-party tools. For example if you use 7-Zip on Windows to unzip multiple archives, there is only one progress window and progress bar, and it will display the names of each archive being extracted one after another.
That's true, but I'd argue that a window that appears and disappears within substantially less than one second is often a bad idea anyway. Progress indicators are for things you wait on.
Apple disagrees - the Finder already handles this without any visual feedback for file copy operations - you don't get a file copy progress dialog if it takes less time than you need to react (just an audio confirmation).
J Nielsen would disagree with you. A subsecond operation could very well operate without visual feedback and only after that start showing the progress. Does finder have a way to show messages in status bar or some such? For quick ops it would be ideal to say, "operation completed".
