There is something curios about the throne room of God as experienced by Isaiah. First, there were strange, winged creatures that used two sets of their wings to cover their faces and their feet. Why is this important? It shows God's holiness. Even these creatures who were proclaiming praises to His name could not look at him because of His holiness.
Secondly, Isaiah was distraught over the fact that He saw the Lord. Isaiah understood something that the people of the day did not understand: our sinfulness pales in comparison to God's holiness. We cannot see God because His pure holiness would strike us dead on the spot (that's why Moses only got to see God's backside). Isaiah was grieved ("Woe is me!") from seeing God because he knew that the payment for this was death. But God, in His mercy, did not strike him dead. No, God had other plans for Isaiah, but what Isaiah showed here was a proper understanding for his place as it came to his heavenly Father. A true understanding of God's character starts with a deep respect for His holiness – a respect that marked Isaiah's life.