"Mr. Darcy had at first scarcely allowed her to be pretty; he had looked at her without admiration at the ball; and when they next met, he looked at her only to criticise. But no sooner had he made it clear to himself and his friends that she had hardly a good feature in her face, than he began to find it was rendered uncommonly intelligent by the beautiful expression of her dark eye". (Ch 6)

He changes his mind and, when asked, he makes his admiration clear(as his indifference before).

I don't know if he finds pleasure surpring and dissapointing Miss Bingley, but we do, don't we? ;-)