Child-sacrifice is fairly standard for the ancient world, so leave that aside. The scary shocking part is that Avraham had no idea that he was going to have to sacrifice Isaac; he's got one child left (God told him to send the other one away into the wilderness, and that was that for Ishmael), it took an awfully long time to get that one, and he's awfully fond of the kid. And God says, go sacrifice him. God even rubs it in, reminding Avraham that Isaac is his son, his only son, the one he loves. And God strings Avraham along until the crucial moment, and then says "just kidding."
This is the scary shocking bit - that God could be so awfully mean. It doesn't even turn out okay in the end - in the midrash, Sarah is so horrified that her soul leaves her, and Isaac develops some kind of speech disorder (and no wonder). Isaac is alive, but the family is broken.
At this point, the sermon either extols the virtue of doing exactly what God tells you, or finds some way to gloss over the nasty bits and pull out some kind of comforting platitude.
However, let's look at the liturgy for a second. Specifically, the Unetana Tokef, which says that in the next ten days, God is going to decide who shall perish by fire and who by water, who by sword and who by beast, who from hunger and who from thirst, who by earthquake and who of plague, who by strangling and who by stoning - and so on. And the thing is that God doesn't play fair. Avraham ended up with a broken family; we all know of bad people who prosper and good people who suffer.
In fact, God can be mean, and God doesn't play fair when deciding to whom to be mean. The raw horror of the Akedah story is the raw horror of the Ten Days of Penitence which start on Rosh haShana - this year, bad stuff is going to happen in senseless ways. People are going to die in fires, be drowned by tsnunami, starve on the streets, die in earthquakes, get horrible diseases - it's not going to be nice and it's not going to be fair. Sanitising the story, choosing to focus on the inspirational parts of it, making it comforting, stops that message coming across.
The blast of the shofar is supposed to awaken our souls to action. In choosing the most unpleasant story in the Torah, the rabbis give us an emotional blast. We don't cover our ears when the shofar is blown; we shouldn't try and make the story of the Akedah nice. BAD STUFF IS GOING TO HAPPEN TO PEOPLE WHO DON'T DESERVE IT, and it might be you, but you don't know it. It might be you, and empathy breeds sympathy; if it was you dying of cancer, how would you want people to behave towards you? If it was you starving to death, how would you want people to treat you?
Ten days of discomfort, people. Our tradition says we need shaking out of our comfortable ruts once a year. It's not about being uplifted, it's about being disturbed, and appalled, and horrified, and jolly well shaken into being better people.