> Developers uses powerful macs and users have old windows - the usability is different, but devs usually don't care. Works fine on my machine!

Part of what QA testing should be about: performance regressions.

Usually it is not a priority, especially for enterprise software. It's ok if UI is lagging, page finish loading in 10 seconds, etc. Simply because there is usually no other choice, people have to use whatever is bought/developed.

This is not even a regression - it has always been there, unnoticed!