Consider if you will examples of "sameness" used in today's society. School uniforms would be a place to start. One of the most prolific rationales for school uniforms is the idea of "sameness." Uniforms equal the playing field, and so there can be no judgements against students based on personal style, socio/economics, and etc. Students have the opportunity to learn and achieve as equals. That would be a positive for a society such as Jonas lives in.
I agree with Post 2, but I think that it goes deeper than that. The eradication of "stirrings" and strong emotions would make a community a much less violent place. There would not be bullying or domestic abuse, or any of those sorts of things that plague us in our societies today.
Of course, taking away people's humanity in that way has huge costs. But it would make for a much more orderly community.
The argument could be made that the degree of "sameness" portrayed in The Giver would greatly simplify life in contemporary society. If clothing was uniform for a given age group or occupation, there would be no need for concern about changing fashion, gang attire, jealousy over more expensive clothing, and so on. In the same sense, there would be no need to worry about obtaining a better car than the neighbor, having a nicer house, or placing your kids in a better school. Socioeconomic differences and conflicts would become nonexistent. Theft would decline in frequency because everyone's possessions would be the same, creating no attraction to take something from someone else.