Evangeline posted an interesting post about character growth (among other things) yesterday. She wrote, "...I'm not seeing books like that on the shelves anymore... character growth is next to nil. And it's been replaced with fighting against physical attraction and sex and personal agendas insteady of the falling in love part assisting the protagonists in GROWING with those attributes."
I have to agree that character growth is the most important part of a romance. Love is what makes the plot go, but if the characters don't grow, the book is essentially dull, no matter how many sex scenes you try to spice it up with.
I've always believed readers love romance because of the way the characters grow and change. I've written a couple of books that some reviewers didn't like because the characters were abrasive or just plain obnoxious at the beginning of the book-- but to me, the more problems the character has at the beginning, the more potential for growth. (Within reason, that is. A book with a wife-beating hero doesn't work for me; even if he changes his ways by the end of the book I'm unlikely to believe in the HEA.) But the characters' problems must be genuine, not just minor little roadblocks the author tosses in to get the manuscript up to 100,000 words. The drama of character growth is more pronounced if the characters have some really serious issues to work through.
Of course, to be believable, a really bitchy, snarky heroine can't turn into a sweet angel by the end of the book, and an alpha hero can't turn into a beta. Character growth isn't about making imperfect characters perfect. It has to be a convincing metamorphosis, and we have to see the growth-- the heroine can't hide herself away in a cocoon, only to later emerge a beautiful butterfly. But the joy of romance is that neither character has to do it alone. In romance, the hero and heroine can confront their demons together.