I have accumulated my researchat the page linked below, but I am far from happy with my presentation of it, and the issue is going to probably consume the rest of my philosophical career 
What it boils down to in my mind is that:
1 - Plato and others had established a philosophical consensus in which pleasure could NOT be the guide of life due to a variety of *logical* arguments, especially that the desire for pleasure can never be satisfied, and that "something more" is needed in addition to pleasure.
2 - Epicurus knew that in addition to proof by pointing out that all nature at birth cries out for pleasure and against pain, he had to defeat the anti-pleasure *logical* arguments.
3 - What people (especially stoic-friendly people who are suspicious of pleasure) focus on today as "ataraxia" is nothing more than the commonplace observation that the maximum quantity of pleasure any living being can experience is that quantity he experiences when his experience is totally "full" of pleasures, without any mixture of pain left behind. This is a *logical* construct that shows that the desire for pleasure CAN be satisfied, and that nothing MORE is needed for the highest possible state of existence. No ancient Epicurean would have failed to understand that this is a debating device, because elsewhere, and otherwise, Epicurus was totally clear that *pleasure* as commonly understood is the goal of life.
4- But due to the tragic victory of Stoicism/Judeo-Christianity/Platonism, the victors got to write the history, and they erased virtually all of the foundation and context, preserving only what they wanted to preserve. And of course among the first things they chose to preserve the observation that "simplicity" is frequently the best course for maintaining steady pleasurable living. And worst of all, they ripped "absence of pain" totally out of context to imply that there is some mysterious "state" that his higher and different from ordinary pleasure which we should set as our goal -- transforming Epicurus directly into an anti-pleasure / anti-pleasure more potent than most of their own Stoic perverters of Nature! And THOSE two things (1 - simplicity, and 2 - the alleged goal of "painlessness") is all that 98% of people think is significant about Epicurean philosophy today!