Regarding giving up after 500ms: I don't think the issue is that people are consciously abandoning a site after a single page load that seems a bit slow. It's the cumulative burden of slightly slow pages that make the site slightly less attractive compared to other alternatives that respond faster. The differences are noticeable - if only subconsciously - and the result is that a portion of the users will move to the other service that just feels more responsive. Responsiveness of the site is part of the value being offered (even if people don't recognize it explicitly) For any site with significant volume of users and some effective competition for their service, this distinction results in measurable changes in use/conversions. I think the _actual_ change in user activity or conversions for s specific site would depend a whole lot on the nature of the service being offered and the alternatives available.