In my experience, that which kills "snappyness" for commercial sites is primary annoyingly slow industry standard ad- and traffic-tracking-systems, and secondar

In my experience, that which kills "snappyness" for commercial sites is primary annoyingly slow industry standard ad- and traffic-tracking-systems, and secondary layout rendering issues due to complex css or silly number of images. (Lesson learned: make sure you can serve pages without ad and tracking scripts to show the customer that you are fast as hell, that it is their "money-maker dependencies" that kill snappiness) Javascript can often be hidden behind some user-initiated click, where it "feels" okay to have 1 or 2 sec of delay given that some feedback is given directly, such as changing the mouse pointer or the color of the button pressed. I wish github would let me be the initiator of more of their page updates, because those pages can be really slow to finish using my weaker machines.