I'm disappointed: I can't see any comments about the awful .zip file integration in modern Windows version.
Extracting the files requires a pop-up or a non-intuitive context menu.
It was slow. Unzipping archived source with thousands of files could take an hour or more... or 15 seconds via pkunzip.
It didn't warn of corruption. Windows-unzip a corrupted file, and it will just stop at the point of corruption with no feedback, as though complete. Using pkunzip you'd get a warning about a corrupted file.
Being that slow, and not reporting errors are two things that really aren't acceptable. I have no idea if it's improved since then.