I don't think that this was an arranged marriage or one of convenience. No evidence really points to that.
I really believe that this is true love. If Felipe were going to marry to please his parents, then he would not have married Letizia. For those of us average beings going through our daily lives, Letizia most certainly seemed to be a catch for any man, but not for the Crown Prince of Spain. She had many things going against her-previously married, divorced parents, said to be agnostic in her religious beliefs, a commoner (when many said that it would be best for Felipe to marry an aristocrat or royal), and I am sure that there are other things that many could add.
When thinking of the history of the monarchy of Spain and the fact that the monarchy under King Juan Carlos is still very young, one would think that Felipe would have had his flings and then finally married for convenience, but that certainly was not the case her, IMO. If Felipe were really going to choose a wife based on that criteria, he would not have chosen Letizia. He must have married her because they were genuinely in love. Given the facts, there really is no reason for Felipe to have chosen Letizia in general other than that they truly shared a connection. Although controversy has subsided somewhat since the marriage, most of us can admit that their engagement had it shares of critics and many of them were opposed to Letizia, because she had a past. Nothing that every person in Spain and the world over are not accustomed to hearing of and some even being a part of on a daily basis, but when we think of royals we kind of like to set them apart from us in certain respects. If you are going to be a member of the SRF and a monarchy is going to exist then its family members must maintain a certain standard that is unlike that of the average members of their country's society. It's not about being better, but actually being royalty and carrying one's self in a certain manner.