I'm beginning to sound like a broken record here... but following Gwen Haye's romance formula is hands down my favorite. It gives such a satisfying romantic arc every time and even though it gets predictable (as most structures do), it's still so much fun to write or read someone who's learned from her method 
Pros for story structure is that it's going to meet the genre expectations. Fantasy/romance/action/mystery whatever genre it is, the readers have certain expectations and it's up to the writer to make sure they fill them.
I don't really have any cons? If people enjoy writing genre fiction then the structures are there to help them make sure any readers will enjoy what they write. If someone wants to deviate too much from genre expectations then they're just not genre writers