Well, I've read it, and I still disagree.
In the case of Flowers, Charlie Gordon seems to be faced with the choice of happiness or intelligence; I argue that blind happiness is not what any individual capable of understanding this article should strive for, but I also don't believe that one should blindly pursue knowledge either. My go to quote for this situation is John Stuart Mill's, "It's better to be Socrates dissatisfied than a pig satisfied." (which can be found in its entirety in paragraph three of [Don't] Lie to Me)
I'd like to point out several factors in Keyes' novel which keep it from fully supporting Adarsh's ideas, and I will try to do so without spoiling the story for anyone. First, Charlie's 'happiness' when he is in his mentally diminished or 'ignorant' state is due to the lack of ignorance in those around him. In other words, in order for 'ignorance is bliss' to work, there must be others behind the scenes who know the whole picture to keep ignorant people happily ignorant... or ignorantly happy. As long as Charlie surrounds himself with people who pick on him but still say they're his friends, he's happy. Those friends of his know that they need to tell Charlie that they are friends to keep the peaceful charade going. As soon as someone new enters the scene who picks on Charlie before stating that he's Charlie's friend, Charlie feels unsafe and scared, certainly not blissfully ignorant. Secondly, a large portion of Charlie's distress stems from an undeveloped emotional mindset meaning that situations which would distress adults without leaving them incapable to work leave Charlie in an unmanageable state of despair, or they make him soil himself. Highly emotional individuals are kept 'ignorant' in order to avoid harm to themselves or others (either physically or from emotional duress). Ignorance is a veil for those who are incapable of understanding the deeper meanings and workings of the world, but to hold on to it after one has matured is like going to one's first job interview with the security blanket he or she had to sleep with as a baby. Yes, security blankets are no harm in it of themselves, but when security blankets can be so easily taken away, no employer would hire someone who still needed one.
Happiness hasn't been a driving force in any of my activities for as long as I remember. I've found that ignorance in any realm has been more detrimental to what, I guess, could be called 'inner peace' than any suffering I've gone through in search of understanding or achievement. This isn't to say that I view everyone who lacks the pervasive curiosity I have that came from genetics and environmental factors as incomplete or misguided, but I feel that America as a society, or at least my generation and the one to follow it, would lean more toward taking the blue pill than the red one.
Ignorance, be it through intentionally ignoring the world around one's self or drugs or what have you, is an all encompassing extension of Marx's "Religion is the opium of the people." But, you may ask me, if 'ignorance is bliss' is an extension of 'religion is the opium of the people,' how can I claim to be a religious person and harp on people who wish to be blissfully ignorant? That's an easy one; my religion isn't used as a crutch to make life simpler or to paint over holes in my understanding of the world. Christianity based in a reading of the Bible that doesn't contradict itself requires me to seek out understanding, and ask questions, and achieve.