I wrote some time ago that the speed a web page loads matters, and now it matters even more as people use the Internet from phones, tablets and other devices that don't always have true high-speed access, nor do users have patience when on the go. Here are some numbers to underscore the need for speed:
Adding half a second to a search results page can decrease traffic and ad revenues by 20 percent, according to a Google study. The same article reports Amazon found that every additional 100 milliseconds of load time decreased sales by 1 percent. Users expect pages to load in two seconds - and after three seconds, up to 40 percent will simply leave
(from Improving UX Through Front-End Performance). As I've said to classes and clients: no one has ever said "this website loads too fast," so hurry it up.