I am a confirmed skeptic of the UN Human Rights Council, but this Foreign Policy article makes a ton of sense. Basically, it argues that the problem with the UNHRC isn't that it is "controlled" by illiberal regimes, in the sense that they have a majority on the council. The problem is that the illiberal regimes that are on the council have invested a ton more diplomatic energy in getting fellow members to vote according to their wishes, while liberal stalwarts have been asleep at the switch. Geographic bloc voting is allowing nations like Sudan, Cuba and Zimbabwe to exercise disproportionate influence on the council's agenda, because they can bring along the votes of even democracies in Africa and Latin America. But if a sufficiently credible liberal power (say, a resurgent United States) could mobilize the democratic regimes to actually vote their values, then we'd see a very different result.
From this perspective, the Obama administration's decision to take a seat on the UNHRC is very important, because it gives a base to do the hard work of diplomatic investment and persuasion which could pay off big dividends down the road. The Bush administration policy of non-engagement is emotionally tempting to someone like me who has wondered if the council is simply a lost cause, but whatever passions it satisfies, it clearly hasn't worked in terms of stemming the poisoning of human rights discourse when the agenda is in the hands of a country like Cuba.
Via OJ, which also links to Freedom House's very interesting "report card" on the UNHRC's work from 2007-09.