Prairie Chick has a problem with Character Arc

I'm having a discussion about character arcs over at Prairie Chicks Write Romance.

How fickle a reader are you? Do you close the book if you don't like the main characters?

Or, do you read on to discover if the hero or heroine has a character arc and will be redeemed at the end?

Do books even need character arcs?

As a writer, I'd really like to know what you have to say on this subject. You can comment here or on the Chick's site, but please, let me know what you think...