[Wowfunhappy]

I can't imagine not having access to QuickLook. It's not really about how quickly apps open so much as the UI—in a large folder of images or documents, I can use QuickLook to see what's inside each one, whereas without it I'd have to open a window for every document.

[kitsunesoba]

Yes, for me the killer aspect of Quicklook is being able to flip through dozens of documents in barely more time than it takes for my arrow keys to actuate. It’s wonderful for skimming through dozens of files quickly. Icons that accurately represent content on more than just images are great too.

Aside from that, QuickLook remains one of the few examples of a generic extensible document reader in modern operating systems. The way it gains the ability to read new types of files just by virtue of the owning app’s bundle being present on the system (no installation necessary, and it goes away when you delete the app) makes so much sense, and it’s a shame that there’s no equivalent on Windows and Linux.

[Wowfunhappy]

> QuickLook remains one of the few examples of a generic extensible document reader in modern operating systems.

...were there other ones in classic operating systems? QuickTime <= 10.2 did let you install third-party components (I wrote one recently), but what else was there?

[mixmastamyk]

The Amiga pioneered this with datatypes.

[kitsunesoba]

There was OpenDoc on classic Mac OS, and I think maybe COM on the Microsoft side of the fence? Not as well versed on Windows stuff though so that may be a misread on my part.