I personally don't like the "How would you know what love is if you never experienced it's opposite?" arguement. I simply find that is a rather poor one that people use because the Biblical answer is just so confounding.
Apart from that I agree with your post. I agree that God has a good plan for all of us. I also strongly support the idea that only those who reject Christ will really be in trouble. And that in Christ, suffering becomes a tool for good.

But now to the question of WHY? Why did God allow sin to enter the world... why not make a sin free world from the begining? We know He can because that's where we're going when Jesus appears... so why this suffering filled world before hand?

Two passages give the tough answer. I'll quote them both below. In approaching these passages our human sense of justice will be challenged, but we know that God is good and there is no evil in Him and that His ways are not our ways and that He knows what He's doing in ways we can't begin to understand. We need to trust that He knows what He's doing... even when we struggle to understand why.

To the passages:

Romans 9:14What then shall we say? Is God unjust? Not at all! 15For he says to Moses,
"I will have mercy on whom I have mercy,
and I will have compassion on whom I have compassion." 16It does not, therefore, depend on man's desire or effort, but on God's mercy. 17For the Scripture says to Pharaoh: "I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth." 18Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.

19One of you will say to me: "Then why does God still blame us? For who resists his will?" 20But who are you, O man, to talk back to God? "Shall what is formed say to him who formed it, 'Why did you make me like this?' " 21Does not the potter have the right to make out of the same lump of clay some pottery for noble purposes and some for common use?

22What if God, choosing to show his wrath and make his power known, bore with great patience the objects of his wrath—prepared for destruction? 23What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24even us, whom he also called, not only from the Jews but also from the Gentiles? 25As he says in Hosea:
"I will call them 'my people' who are not my people;
and I will call her 'my loved one' who is not my loved one,"
26and,
"It will happen that in the very place where it was said to them,
'You are not my people,'
they will be called 'sons of the living God.' "

There it is... a bit mind blowing really... but this is our loving Father.. and we need to trust Him. He knowingly and willfully and deliberatly created some people for destruction. He knowingly and willfully and deliberately created others to receive His blessing and glory. He did this to make His name known in the earth and to display both his power and glory in his wrath and mercy. Neither those destined to destruction nor those elected for salvation deserved to be saved. Everything that the elected ones recieve comes from God's MERCY!
God's election of the damned to damnation is not something that God does lightly nor takes any pleasure in. He is neither cruel nor heartless.... in fact He willingly gives His very own son to save those very men... but they would have none of it.

this leads us then to the next passage:
Hebrews 5
1Every high priest is selected from among men and is appointed to represent them in matters related to God, to offer gifts and sacrifices for sins. 2He is able to deal gently with those who are ignorant and are going astray, since he himself is subject to weakness. 3This is why he has to offer sacrifices for his own sins, as well as for the sins of the people.

4No one takes this honor upon himself; he must be called by God, just as Aaron was. 5So Christ also did not take upon himself the glory of becoming a high priest. But God said to him,
"You are my Son;
today I have become your Father." 6And he says in another place,
"You are a priest forever,
in the order of Melchizedek."

7During the days of Jesus' life on earth, he offered up prayers and petitions with loud cries and tears to the one who could save him from death, and he was heard because of his reverent submission. 8Although he was a son, he learned obedience from what he suffered 9and, once made perfect, he became the source of eternal salvation for all who obey him 10and was designated by God to be high priest in the order of Melchizedek.

Jesus takes on our humanity that He may understand our weakness and make appropriate and compassionate atonement for us. The clincer here is that through suffering he learnt obedience. This is how God has designed the present world. Adam wasn't just punished for his sin... he was set up to lean obedience through suffering. It's a bloody tough lesson and the suffering is so overwhelmingly harsh as to be really beyond our comprehension. Nevertheless, when we get to the end... we'll be able to appreciate what God has done. Until then, we are really asked to take it on faith that God knows what He's doing.

If you want to take issue with it...or even if you just want to get a better understanding of it.... read the book of Job. Particularly from chapters 32 to the end... where Elihu speaks for God and ultimately God speaks to Job personally. "FAR BE IT FOR GOD TO DO EVIL" Elihu declairs and at the end of the day... Job doesn't get his answer to WHY GOD?... but he does learn to be appropiately humble before his holy and wise and all knowing maker.

Blessings
Cat.