I remember reading that Walter Koenig felt this ep showed how the makers of the show didn't give a crap anymore, especially where the character of Chekov was involved. According to him, Chekov was supposed to be the "hip" younger character as compared to Kirk, Spock and the others, and here he is portrayed as an uptight establishment type, and Spock is the "hip" one. I guess he felt Chekov should have been connecting with the "hippies", not Spock.
I don't know for sure how intentional this was, but I think the characterization's of Chekov and Spock in "Eden" were right on. I always felt one goal of this episode was to explore and address the generational divides of the 60's. And the related themes of idealism vs. status-quo.
The thing is not all kids were hippies, and not all adults were square. Some kids were burning their draft cards and embracing the counter-culture, while others were volunteering for service in Viet Nam and functioning within the establishment. (And of course a lot more somewhere in between.) So to me the exchanges between Chekov and Irina make perfect sense. They have completely opposite viewpoints, but being the same age have much in common as well, and their attempts to reconcile these differing philosophies were probably meant to mirror debates that were going on in Universities and within the youth of the time. Making Chekov more 'hip' wouldn't have worked nearly as well in overall context...IMO...though Walter Koenig personally might've leaned more in that direction and felt a conflict of interest in portraying the 'establishment' role maybe, I'm not sure.
Adults the same way. Some couldn't understand or accept much at all of what they felt the younger generation represented, while others were sympathetic and supportive of their idealism but tempered somewhat by age and a sense of what was realistic. (And again everything in between.) So again the exchanges between Spock and Adam, as well as between himself and some of his fellow officers made sense, and were probably trying to illustrate the varying opinions among adults as well.
Come to think of it, it was interesting that almost everyone on both sides of the episode had at least somewhat of a different point of view. Some were hardliners, others simply sure of their beliefs, some still questioning, some in the middle and a couple of them "reached". Not too unrepresentative a micro-sample of society.
The other thing I like is that it was neither a hippie-bashing episode nor anti-establishment. Though I wish the ending had been a little less one-sided.
Not too bad an ep afterall maybe. Except for the music and clothes...those will always be a little difficult. Well, at least no one thought to paint flowers, paisley's or the word "Groovy" on the side of the Aurora's hull.

Mark