[Sprint]

As a user who sometimes has terrible coverage and 2G I would suggest not using AJAX so much. If you do, make sure it is cached by the browser. It is incredibly frustrating to have zero indication if there is some AJAX loading going on in the background or not. The browsers don't show and animated indicators that websites show, well, like to animate for eternity. And if loading stopped or you decide to reload the page in the hope that this time it will load better, sites usually fetch the whole shebang again.

So my recommendations: Make sure your site is split into nice, cachable chunks (css, images, js, etc). If you can, avoid JS. Avoid loading content invisibly to the user in the background.