Ulises > Status Update

Question for all my fellow readers: at what point do you give up on an unsympathetic main character?

Working on a novel right now in which the protagonist is insanely selfish and obnoxious, though her story arc will obviously make her grow up. But "growing up" might not happen until book 2.

So how much obnoxiousness do readers tolerate before saying, "I'm done with this book because the main character sucks?"