|Statue of Abraham & Isaac (Princeton)|
To critique this story, you must do what is required of every sound biblical criticism: understand the context. You can't just read a passage in isolation and pass judgement. You have to ask, "What is the larger context of this story? How does it fit in?" The context includes the rest of the chapter, the rest of the book, and the rest of the bible. It also includes the historical context in which it is written. To get a grasp of this passage, however, all we need is to understand what has happened in Abraham's life until this point.
First, Abraham is called out of his land to travel to a distant land. He is called by God, although we are not told exactly how God communicates with him. We can only deduce that it was very convincing, because Abraham left his home just on the authority of God's voice alone.
Since then, God has radically transformed Abraham's life, making promises to him that were perhaps unbelievable at first, yet (1) were backed-up by the miracles God performed in front of Abraham, and (2) were even at this point beginning to be fulfilled. Most importantly, God promised Abraham a son, from whose seed the entire earth will be blessed. Keep in mind that Abraham was 100 years old, and his wife was not only in her 90s, but had been barren her whole life (she's never had children, despite their trying).
So the existence of Isaac was not only a miracle in and of itself, but it was also the beginning of the fulfillment of a major promise from God. Furthermore, according to God's own, explicitly stated plans, Isaac's life (and his survival until adulthood in order to have children) was really important to God Himself.
All of this must have been in the front of Abraham's mind. God had walked with him for more than 25 years at this point, showing Himself to be a trustworthy God. Abraham knew Isaac was important to God. He must have known his faith was being tested, and he was confident that God would provide.
As a result, Abraham is commended in the New Testament as a model of strong faith. However, usually when we think of Abraham's faith being tested, we think of it as a blind faith. But Abraham's faith was built on nothing less than the miracles he witnessed, as well as the beginning of the fulfillment of the child of promise. No, his faith was not blind, but instead based on evidence. He knew that if God were to fulfill His promises to Abraham, then Isaac could not die (or at least that the God of all creation could overpower death). So he was not blindly jumping off a cliff; he knew there would be a net at the bottom.
The same goes for us today. Our faith, as the bible describes it, is built on the strong and confident trust in Jesus Christ, who has proven Himself to be real and trustworthy, as well as worthy of worship. Universally, the bible does not speak of blind faith, but instead on a faith based on evidence presented to us. The story of Abraham is no different.