Comment by open-source-ux

Users do notice speed issues in apps and websites.

The NNGroup has done studies with users to gather reactions to slow websites in 1997 and 2010. They remain relevant in 2021 to both apps and websites: "Users really care about speed in interaction design" [1]

A few weeks ago someone on HN shared the reflections of the developer of SumatraPDF - a native Windows PDF reader that is small, lightweight and performant (all the things that Adobe Acrobat Reader is not).

From the developer Krzysztof Kowalczyk: "I believe being small and seemingly fast was a big reason for adoption...there will never be a time when users want bloated and slow apps, so being small and fast is a permanent advantage." [2]

[1] Website Response Times (2010): https://www.nngroup.com/articles/website-response-times/

[2] Lessons learned from 15 years of SumatraPDF : https://blog.kowalczyk.info/article/2f72237a4230410a888acbfc...