Better than asking whether God's love is unconditional or not, rather...ask How does God love?
God loves OBJECTIVELY as opposed to SUBJECTIVELY. Now the treatment of people by God is subjective at times, yes. But he loves objectively. Hmmm...what doth I mean.
Objective loves bases the integrity of the love not on the subject of the love (for example, your boyfriend, girlfriend, children, husband, wife...etc) but on the one doing the loving. God loves objectively. He doesn't love us because we are or are not lovable but because of He has determined to love us. This might best be expressed as IMPERSONAL LOVE.
Subjective love is love we humans all too often experience. It comes and goes based on the subjects we love. Whether it be a person, a hobby, job and so on the love we have for such subjects often vacillates with its desirability. When the subject of our love is most pleasing we love it most and when it is unpleasant we love it less. This might best be expressed as PERSONAL LOVE.
This is why we are commanded to love with divine love, so that our personal preferences and prejudices are removed and the integrity of the love we have for another is not based on their performance or desirability but our integrity and choice to love.
Hence, God's love is based in HIS integrity. Does this mean God does not respond with love but that He is a machine that just loves like a Robot? Of course not. It is to make clear God does not love as a human loves, He is God and it is His integrity that guarantees His love. The very reason those born again, those possessing the righteousness of Christ are double recipients of God's love. Because in that case not only are we the recipients of God's impersonal love, his objective love but as well a unique form of Divine Personal love (remember not human subjectivity). Because by possessing the righteousness of Christ God automatically responds to His Own Divine Righteousness with Personal Love.
Feeling Love By God now? I hope so.