IMHO, the United Nations is simply trying to look out for the welfare of the human race, while at the same time creating a concord between all nations so that tensions will not arise. Don't get me wrong, conflict will still come about. But the UN provides a strong, neutral medium where nations may civilly come to a conclusion on how they may solve problems.
In addition to this, it organizes the issues of our world into different subcommittees in which such issues may be looked at a litte more closely. Though the Security Council (one of the minority of committees in which specific nations have veto powers) is the most famous (or infamous, depending on how you may interpret the situation), at least 100 other committees exist. These groups discuss social and economic concepts, create healthy alliances - NEPAD and ASEAN, for example - and decide on the best course of action.
The UN has created a Millennium Goal, which stresses that for 10 or so years, the number one goal would be to achieve sustainable development. Because the UN has concentrated on doing so, I can see where it may come across as "too nice".. health care, landmine clearance, education, infrastructural improvements. Not exactly anything to do with politics. But collectively, everything that has been accomplished has made a large difference in the world, and that should definitely be something we should look at.
Overall, I just don't think we should judge the UN on the basis that it hasn't done as much as it could have in solely the Security Council. Other committees have added greatly to the progress of our world.
Yay for multilateralism

- My 10 cents, in binary, that is