Love, personified in Eros, thus "is by nature neither immortal nor mortal. But now he springs to life when he gets his way; now he dies—all in the very same day", as Plato vividly and imaginatively has his character, Diotima, describe it (203e). In the same vein, according to her, love is neither good nor bad, and neither wise nor foolish, and cannot be, for love goes along with desire, and desire is always for something you don't have; what you desire will be something good, and beautiful, and so there can't be love without a lack, and longing, for that which has importance and value, which is beautiful, and good for you. At the same time, (unfortunately) love can equally not be without the danger of being carried away from what reason dictates.
It is this ambivalence of love that Socrates is the first to bring up when it is his turn to speak at the drinking party that gives the Symposium its title. Attributing to love the qualities that love aims at (such as beauty and value) wouldn't be true to how things really are: love may be love for such things, but love itself is constituted by desire, not by the desirable. Of course, there is a way to put these drives to a good use and finally arrive at the good and beautiful in a proper way, according to Socrates. He reports having learned this 'art of love' as a young philosopher from Diotima, a priestess and his teacher: the famous 'ascent of love', certainly one of the most beautiful and ingenious pieces of philosophy that have ever been written.
However, I am myself more concerned with the problem than with Plato's solution. I'm interested in the role that beauty and value play in the strong pull that love and desire perpetually exert on us, and in why and how (unfortunatly) this can get in conflict with the more reflective and reasonable lines of activity which we employ in living our lives. (To be sure, that is certainly a curiosity I have in common with Plato, and quite probably any other philosophically-minded person as well. But I'm more than hesitant to follow him in some of his metaphysical moves, and therefore, beautiful though his solution is, I've never been able to become comfortable with it.)
 Plato, Symposium, translated, with introduction and notes by Alexander Nehamas and Paul Woodruff, Indianapolis: Hackett 1989. All Plato quotes are from the Symposium in this translation, unless otherwise noted.
 In Plato, the good and the beautiful are genuinely in harmony with each other, and therefore never in real conflict; and they're both equally of supreme reality compared with the world of things and persons which we inhabit. Although I find that many elements in his analysis ring true, I wouldn't map them onto the metaphysical layout in that way: very roughly, I think that on the contrary beauty belongs at the far side of unreality, while what makes our lives successful (that which Plato would call the good) is attained by generally steering close to reality, and so there is a perpetual tension here that must be reflected in a metaphysical conception.