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.