I just finished "Childhood's End" with mixed feelings. I love Arthur C Clarke's ideals and visions of the future. 2001: A Space Odysseus is one of my favorite books.
As I was reading Childhood's End, I grew to like the Overlords more and more. They ushered in a new era of peace, teaching humans to stop hurting each other and abusing their environment, and making the world a utopia. I'm Buddhist, and for a while I saw the Overlords as a sort of boddhisatva who created a Pure Land right here on Earth. But that's where the spiritual references end for me.
The ending was quite a twist. Instead of helping humans reach enlightenment, the Overlords played the role of the Pied Piper, leading the children away! The Overmind comes across as cold and non-compassionate, not something I see as an ideal next stage in evolution. It's like a mental version of Star Trek's Borg, assimilating minds into itself while leaving death and destruction in its wake. The material world is no longer important - the Overlords seemed so concerned with preventing animal cruelty earlier, but once the children are assimilated they don't even leave the Earth to the animals to allow other species to continue to develop. They caused the whole solar system to cease to exist!
The last of the humans no longer lived in peace and prosperity ever since the children were taken. They destroyed themselves in war and desperation as the human race came to a bitter end. Neither the seemingly benevolent Overlords or the Overmind seemed to care - all they were interested in was the children. Yet other than experimenting with their "powers", which were really rather scary, no explanation was given for why the children were "better" than humans.
I felt it was more a way of using humans, then discarding them, rather than helping humans attain their highest potential in the next stage of evolution. I would rather see humans develop the way the Overlords did - with compassion and benevolence, developing technology and travelling to the stars.