25% gain here Puntuado con 3 de 5 estrellas

I've tested 'Firefox Preloader 1.0' on Firefox 6.02 and now on Firefox 7 Beta6, with 60+ add-ons. Platform is Windows XP SP3, computer is old (Duron CPU at 1.6 gHz!), Windows Prefetch is on for boot only (hence Firefox not concerned):
Cold starts of course,
FF 6.02: Without Preloader: 21sec -- With Preloader: 16sec
FF 7 Beta6: Without Preloader: 12sec -- With Preloader: 9sec
That leads to a gain of 25% with Preloader;
Shows as well how faster to start Firefox 7 is. Extra delay on boot with Preloader is not noticeable (does exist slightly perhaps but perception of time is as we know subjective)

Esta valoración es de una versión anterior del complemento (1.0.1-signed).