To me, the real turning point is if and when we learn how to precisely control our personalities - in short, reengineering human nature itself. Of course there's the nature vs nurture matter in this, not to mention all the potential factors than even go into a personality, let alone alter it. But I'm 100% against uncontrolled transhumanism, or even mere unregulated genetic modification or augmentation.

Though, let's suppose there was a way to correct obviously harmful behaviorial defects with at least a partial genetic basis, particularly behavior every society would see as egregiously harmful, and especially criminal (supposedly anti-social personality disorder- such as psychopathy - is one of these). Would the prospect of even reducing that behavior be worth it?

I think the real question is how do we retain information better, if that would happen, then surely you don't need someone to actively remind you of hidden information. If I retained 1% of the stuff I've read in the past, I'd be the equivalent to an encyclopaedia. I write tutorials sometimes, and my ability to write good ones has never depended on the presence or absence on participants.