I think the reason why the New Testament condemn Esau for selling his birthright is to remind us that even with grace and marci, and repentance offered to us we have to still remember to be careful of the choices we make. Since,we have to live with making the wrong choices and even repenting wouldn't take away our wrong choice or fix them.
I think selling the birthright represent selfishness, no patients, little faith and one track of mind that lead to making a choice that was only seeing (right now)situation that was in front on him (being hungry) and not at the big picture (what having his birthright ment).
I think this transaction said that Esau's character and values were in the wrong place; he thought about how the stew was his favorit meal, how hungry he seem to have become once smelled and seeing what his brother was making. How his responsiblity of God's work for him was choosen for a bowl of stew. I also think that Esau didn't think of how his father would one day die and will be leaving the birthright down; but on the other hand he didn't have his mother telling him as she told Jacob about the meaning of the birthright.
I think Jacob's character and values reveal his greed, manipulator, and being prideful. His mother has spoken to him about how his brother would rule over him and he may have resented that and began plotting how to change the fact that his younger brother would be over him.