To deny that God's love for us (i.e., adoption love) is "unconditional love" is a strange and provocative thing to say. But I'm convinced it's true. In his book Seeing with New Eyes, David Powlison writes:
I'd like to propose that God's love is much different and better than unconditional. Unconditional love, as most of us understand it, begins and ends with sympathy and empathy, with blanket acceptance. It accepts you as you are with no expectations. You in turn can take it or leave it.
But think about what God's love for you is like. God does not calmly gaze on you in benign affirmation. God cares too much to be unconditional in his love.
[...] Imagine yourself as a parent, watching your child playing in a group with other children. Perhaps you are observing your child in a nursery or a classroom, or on the playground, or in a soccer game. You might accurately say that you have unconditional love for all the children in the group. That is to say, you have no ill will toward any of them; you generally wish them well.
But when it comes to your own child, something more goes on. You take much more notice of your own child. Injury, danger, bullying, or injustice arouses strong feelings of protection -- because you love your child. If your child throws a tantrum or mistreats another child, you are again aroused to intervene -- because you love. If your child thrives, you are filled with joy -- again, because you love.
[...] The Lord watches you. The Lord cares. What his children do and what happens to them matter to him. His watching, caring, and concern are intense. Complex. Specific. Personal. Unconditional love isn't nearly so good or compelling. In comparison it is detached, general, impersonal. God's love is much better than unconditional.
Even though Powlison doesn't specifically mention adoption, he's talking about the theology of adoption: the love that God places on His own children, children that He added to His family through adoption. The following section highlights some parallels to human parenting (and human adoption):
God's love is active. [...] He's involved. He's merciful, not simply tolerant. He hates sin, yet pursues sinners by name. God is so committed to forgiving and changing you that he sent Jesus to die for you. [...] God is vastly patient and relentlessly persevering as he intrudes into your life.
God's love actively does you good. His love is full of blood, sweat, tears, and cries. He suffered for you. He fights for you, defending the afflicted. He fights with you, pursuing you in powerful tenderness so that he can change you. He's jealous, not detached. His sort of empathy and sympathy speaks out, with words of truth to set you free from sin and misery. He will discipline you as proof that he loves you. God himself comes to live in you, pouring out his Holy Spirit in your heart, so that you will know him. He puts out power and energy.
God's love has hate in it too: hatred for evil, whether done to you or by you. God's love demands that you respond to it: by believing, trusting, obeying, giving thanks with a joyful heart, working out your salvation with fear, delighting in the Lord.
[...] Such real love is hard to do. It is so different from "You're okay in my eyes. I accept you just because you're you, just as I accept everybody. I won't judge you or impose my values on you." Unconditional love feels safe, but the problem is that there is no power to it. When we ascribe unconditional love to God, we substitute a teddy bear for the king of the universe.
(All emphasis using bold-italics is added.)
The love God has for each of His (adopted) children is the love of a perfect parent to His own child. As Powlison says, this is not mere sympathy, and it isn't gentle, smiling beneficence.
Human adoption should be the same way. It isn't primarily a good will gesture or a humanitarian act. It's choosing to love a child as a member of your family -- the way God loves us as members of His own family. Consequently, all the benefits of family-hood (the benefits that make kids smile and the benefits that make them cry -- and make them better) -- all these benefits are part of true adoption.
You can read more about Powlison and his contributions to the Biblical Counseling movement at this post on the blog Between Two Worlds.