Artificial-Intelligence Government
The question asks what a utopian society would be like, not if it works, so I'll answer that. I don't think an entirely utopian society will ever work with humans, especially as we are.
First, I'm surprised that no one has brought up AI. There would be a perfectly unbiased, benevolent planetary AI overseeing the world, in charge of all production, agriculture, and distibution. It would also keep close tabs on the environment, of course.
The government would be mostly fascist, with the AI in charge. It would prevent all murders, provide therapy, and all the other things that governments usually provide. At this point we would have quite a few pyschological treatments(brainwashing?), not too mention genetic ones.
Humans would be free to do whatever, as long as they don't infringe on others rights. Socializing, researching, recreation, taking trips across the solar system. Each person would be entitled to a certain amount of mass
This would probably be possible in a couple hundred years, if we actively pursued it. A problem would be overpopulation... no kids for people, I guess. People would still experience hurt in relationships, and problems with their social life maybe, but I don't see anyway to overcome this.
Most of this comes from those Reality Dysfunction books by Peter Hamilton, now that I think of it.
To tell the truth, if I didn't have to struggle to do anything, my life would lose it's meaning. If everthing was perfect, humans would probably turn into hedonistic slobs... but then, slobs makes the society unperfect.