Well, within the constraints of human nature, some societies seem to have much higher levels of trust than others; in some communities you can leave your doors unlocked while you leave your home for a vacation, in others people take practically feudal levels of fortification to feel safe from their neighbors. Crank up the levels of trust and transparency and bring as much of the world as is sustainable to a first world standard of living and you may have the best we could do with present day technology.
Lack of transformative technologies pretty much precludes bringing the whole world to an industrial standard of living in the long term (or even keeping the current first world population living at that standard indefinitely,) but we might be able to stay within sustainable levels if in general our goods were designed to be as enduring as possible and geared towards reuse rather than recycling. Goods production would be lower, so the economy would have to be much more service oriented. This isn't the sort of thing I generally bother with even back of the envelope feasibility calculations for though, since even if it turned out to be totally feasible in principle to build a sustainable global society at first world standards with present day technology, getting society to adopt the necessary changes would be practically impossible, so transformative technologies are a safer bet.
Also, I'd expect both gradual and dramatic improvement in technology. It took until the middle ages to figure out that people needed left and right shoes rather than an identical shoe for each foot. It took until very recently to figure out how to make reasonably cheap computers and that they should be linked through search engines.
There is no reason to think that we're close to inventing all the possible cool stuff.
Assume for the time being that it will forever remain beyond the scope of science to change Human Nature. AGI is also impossible, as is Nanotech, BioImmortality, and those things.
Douglas Adams mice finished their human experiment, giving to you, personally, the job of redesigning earth, and specially human society, according to your wildest utopian dreams, but you can't change the unchangeables above.
You can play with architecture, engineering, gender ratio, clothing, money, science grants, governments, feeding rituals, family constitution, the constitution itself, education, etc... Just don't forget if you slide something too far away from what our evolved brains were designed to accept, things may slide back, or instability and catastrophe may ensue.
Finally, if you are not the kind of utilitarian that assigns exactly the same amount of importance to your desires, and to that of others, I want you to create this Utopia for yourself, and your values, not everyone.
The point of this exercise is: The vast majority of folk not related to this community that I know, when asked about an ideal world, will not change human nature, or animal suffering, or things like that, they'll think about changing whatever the newspaper editors have been writing about last few weeks. I am wondering if there is symmetry here, and folks from this community here do not spend that much time thinking about those kinds of change which don't rely on transformative technologies. It is just an intuition pump, a gedankenexperiment if you will. Force your brain to face this counterfactual reality, and make the best world you can given those constraints. Maybe, if sufficiently many post here, the results might clarify something about CEV, or the sociology of LessWrongers...