I don't really have a lot to add that pro or doc or allan haven't already touched upon. there's no question that roddenberry was a socialist, but I wouldn't go so far as to call him a damned dirty hippie. I would have to say that the trek was definitely a labor of love for him and as such embodied his hopes for utopia, but there was occasionally a tinge of skepticism mixed in there (the TOS episode with the hippies comes to mind). it's important to remember that most of what we call 'socialism' today is viewed through a decidedly postmodern lens by both its proponents and detractors, while roddenberry's philosophy was modernist throughout; he was perhaps one of the last modernists in sci-fi. also, roddenberry's commitment to his vision of the future didn't always resonate with the pendulum swings of the culture around him and rarely went over well with the production teams with which he worked, which means that as time wore on, inconsistencies developed of all sorts.
the battles for creative control between roddenberry and the writers and producers that defined the post-TOS period and the early films made it hard for him to keep asserting his particular philosophy, and you can definitely see the federation vacillate between more and less militant postures from film to film. as pro pointed out, TNG was an attempt to reconcile roddenberry's dreams of the ideal future society with the culture of the 80s. initially you see all the trademarks of roddenberry - insistence upon pacifism (until shit hits the fan about thirty-three minutes into most episodes), deconstruction of the 'supernatural' in all its forms, and championing altruism at both the individual and societal levels.
but as the 90s came along, roddenberry's optimism appealed to fewer and fewer people. the latter seasons of TNG (let's say seasons 4-7) are a study in maintaining relevance in what would otherwise have rapidly become a laughably dated franchise; remember that this time around the campiness and saccharine idealism of TOS were exactly what the producers were hoping to avoid! ira steven behr and the other creators of DS9 cranked the cynicism dial to eleven, which is immediately apparent once you see how the ferengi (intended to be a cautionary tale in roddenberry's socioeconomic morality play once the producers of TNG realized they'd never be taken seriously as an enemy race) take on an increasingly prominent and audience-sympathetic role.
I intentionally left voyager and enterprise out of this particular analysis because in my professional opinion (which has been verified by extensive research) voyager blew innumerable goats and the continuity rape that was enterprise cannot be forgiven. the TNG-cast movies are, for the most part, an acceptable compromise between roddenberry's vision and the zeitgeist of the late 90s/early 2000s - many of the inconsistencies can most directly be attributed to changes in the writing and production staff. of course, the reboot was a reboot, and in most ways was intended to make the trek appealing to non-trekkies; the necessary appeals to 'relevance' seem to have precluded concern for the original vision, but considering how well the film was received perhaps that's not all bad. long story short, the trek was and is and will continue to be filtered through the culture and the times, and it seems less important to discuss whether or not its depiction of society is prescriptive of a particular socioeconomic ideal than to discuss how its depiction of society is descriptive of its creators and of the culture in which each successive chapter of the ongoing story originated.
