The original ending of the play in which Nora leaves her husband (and therefore her children) works from a literary standpoint. Ibsen's play ushered in realism in modern drama, and the ending is realistic in that it grows naturally out of the characters, their relationship, and the situation within which they act and react. There is no romanticism in the play's conclusion, no tender reconciliation between Nora and Torvald as his selfish nature is suddenly transformed. He begs Nora to stay and promises their life will change, but nothing in his behavior two minutes before--or during all their years together--gives Nora any reason to believe him.
Some critics suggested at the time that Nora's leaving was not realistic because a woman in real life wouldn't leave her children (http://www.enotes.com/dollshouse). However, Ibsen lays a solid foundation for Nora's leaving. She has defied social convention--and the law itself--before, in order to save Torvald's life. In the play's ending, she defies convention once again to save her own life and self-respect. Nora leaves quite simply because her last hope in Torvald has been destroyed. He does not know her, he does not value her, and he does not love her. Nora's leaving is shocking but consistent with the play's primary theme concerning human dignity.
The original ending is tough. Most women don't abandon their children (whether that's fact or fiction), but that is what Nora does. So, you as the reader have to decide that in order for Nora to be an actual person, not a puppet plaything of her husband's must she leave the children in addition to her husband? Are the children merely playthings for Nora? And you must decide if that's a feminist agenda and indeed, is this a feminist play (Ibsen says not)?
Nora enters a man's world to save her husband but in the end is not forgiven for this act. Must she leave husband AND children to prove that she's an intelligent, competent person?
The ending provides more critical thinking and elusive questions. Perhaps that is why Ibsen was forced to write a different one.