Given that the Great Leap Forward ended decades ago, I hardly think that it will have any effect on China from here on out.
As far as effects that it had in the past, this program must surely have set China's efforts to modernize back by many years. There is no way to say how many years that would be, though.
The Chinese people were affected by it in that so many of them died and in that their country remained poor longer than it had to. Chinese communism is still there, though you can argue that mistakes such as the Great Leap might have made them more eager to embrace a freer economic system as they have.
Mao launched the Great Leap Forward, an economic and social campaign, in 1958, that aimed to industrialise China and transform it from a backward, agrarian country to a modern nation. A policy of rapid industrialisation and collectivisation was advocated, large amounts of funds were used to construct huge state enterprises for steel production, peasants were encouraged to establish small-scale backyard furnaces to produce iron and steel, and communist organisations, known as the “People’s Communes”, were set up, where private ownership was abolished. Wooden doors and windows were burned to fuel the fires in the furnaces and domestic household items melted to produce metal. This was a huge waste of resources as the steel produced was often of low-quality and thus could not be used in industrial activities. Residents of the communes not only had to work together, they also ate together at canteen. The communes soon ran out of food and faced with a lack of food reserves, large-scale famines occurred. Agricultural innovation, as advocated by Mao, also did not drastically raise grain production. In fact, policies, such as close-cropping, only lowered production rates. State officials, afraid of being punished, provided the central authorities with fabricated statistics that painted a rosy picture. As a result, the government took away more grain from the communes, which were exported to support poorer communist states, while Chinese starved to death. The campaign was a disaster of unprecedented proportions, resulting in a great famine that destroyed 30-40% of houses in China saw more than 30 million people dead at the end of it. Mao’s reputation declined and he was forced to cede the presidency to Liu Shaoqi and Deng Xiaoping, who rose in power within the Communist Party, which led to a change in policy direction.