In the brave new world of SEO there are many areas to consider to tickle the Google algorithms. For many, this is a bit pink and fluffy. It cannot be denied that as Google looks for brands there must be adequate levels of pink and fluff. That said, everything has to be quantified.
In the area of usability, understanding the speed of your site is key. I would recommend going with the horse’s mouth on this one: Page Speed from Google awards your site a score out of 100 along with some recommended corrective action.
Practical SEO where you can measure the output of your developers..perfect!