Besides grappling with the United States on prickly issues like trade and human rights, Xi and his likely deputy, current Vice Premier Li Keqiang, will inherit a daunting array of internal challenges.

Under Hu and Premier Wen Jiabao, China's economy has continued to grow, lifting tens of millions of people out of poverty.

China is now the world's second-biggest economy and closing fast on the United States. But there have been disappointments and discontent along the way, and Hu's much vaunted "harmonious society" is showing signs of cracking.

Chinese leaders have endured a tumultuous year. The veil of secrecy around the party has been lifted, with reports of rifts and infighting. And the fall of Bo brought about China's biggest political scandal in decades.

Bo, once party chief of the massive metropolis of Chongqing, is now in disgrace awaiting trial. His wife, Gu Kailai, is in prison, convicted of murdering a British business associate.

Senior party leaders and their leaders have had to deal with unusual scrutiny of their affairs, with Western news organizations publishing investigations into the wealth accumulated by the families of Xi and Wen.

Chinese authorities responded to the reports by blocking the websites of the news organizations involved: Bloomberg News and The New York Times.

But China's army of censors is having to grapple with the rapid rise of social media platforms on which information moves and mutates at a dizzying pace.

China is treading many fault lines: a widening gap between rich and poor, rising unrest about issues like pollution and land seizures, and a slowing economy that some say is in need of serious reform.

Hu mentioned some of those tensions Thursday along with several other contentious issues -- like food safety, health care and the criminal justice system -- acknowledging that "there are a lot of difficulties and problems on our road ahead."

The Tibet issue

Another issue Hu's government has struggled to tackle during its decade in power is the discontent and unrest among Tibetans living under Chinese rule.

Authorities were given a grim reminder on Wednesday of the disillusionment and desperation of many Tibetans in western areas of China after four people set themselves on fire to protest Chinese rule.

One teenage Tibetan monk died and two were injured after self-immolating in a majority Tibetan region of Sichuan Province, said Penpa Tsering, a spokesman for the Tibetan parliament in exile in Dharamsala, India. And a 23-year-old Tibetan woman died a separate incident in Qinghai Province, Tsering said, citing unidentified people in Tibetan areas.

Dozens of Tibetans are reported to have set themselves ablaze in the past 18 months to express their unhappiness with Chinese rule. And the central government in Beijing is also dealing with other restive ethnic groups, like the Uyghurs in the western province of Xinjiang.

A changing of the guard

Facing up to these difficulties with Xi and Li will be a raft of other newly promoted officials in the upper echelons of the party.

More than 2,200 delegates from across China are in attendance at the congress this week. The congress itself meets every five years. It is designed to assess the country's progress, and set new directions. Every 10 years it selects the new leadership.

The delegates will pick the roughly 200 members of the party's Central Committee, about three-quarters of whom are expected to be replaced, mostly because of their age.

The Central Committee chooses the members of the Politburo, from which the powerful Politburo Standing Committee is selected. The handful of leaders who make up the Standing Committee are China's top decision makers.

Feverish speculation over exactly which leaders will make it into that elite group has intensified in recent weeks.

Xi and Li appear to be sure bets. But the definitive line-up isn't expected to be known until the end of the congress next week, when the chosen few are likely to stride out onto the stage.

They will then have to take up the forbidding task of charting a course for the huge, diverse nation.

Not only will they have to agree on what policies to pursue, according to Guy de Jonquières, a senior fellow at the European Center for International Political Economy, "they must also show that they can implement them effectively, often against strong resistance from within the party's own ranks."

It is still far too early to tell whether they will fare better than their predecessors, Jonquières, who is based in London, wrote in an opinion article for CNN's Global Public Square blog.