The magic of quicklook isn’t really about the behavior in Finder, though. The magic of it is that it’s available as an API to developers. I use an app that is ostensibly marketed as an image viewer but, because it uses quicklook to render file content, it can open all the file types that quicklook supports.

Being able to use an image viewer to cycle files in a zip archive (without extracting them) and be able to render anything from images to spreadsheets to pdf files is pretty remarkable.