Most users don&#x27;t change <i>any</i> settings. Which is why you want sane defaults. I first realised this (very much to my chagrin) when screen-resolution settings were first reported via JS. It was obvious (from the low and poor values selected) that the vast majority of users, under Windows, never right-clicked their desktop and tweaked display settings (800x600 @60Hz on CRTs, or <i>worse</i>, being the most common values).<p>The only users who (in significant number) change settings are power users. A small minority in any regard, but also the ones who then are more likely to defeat various tracking and feedback systems -- disabling feedback or preemptively blocking sites and systems which profile system performance, including Google Analytics, New Relic, etc.<p>Yes, if you can instrument <i>within your tool</i> (Web page, app) for response, great, but that&#x27;s More Work For You, so it&#x27;s far too easy to fall back on standard services. Which your best users are most likely to block....