Quiet a few anime this season have had this major switch from being a light hearted slice-of-life, to a serious drama. Although this isn't something new, it is showing up more frequently, possibly as way to get more viewers. It seem like a weird way to do so, but it might be working and I'm not even noticing.
With that said, approaching anime in this fashion can have its own side effects, both good and bad. A lot has to do with the story and the way it is paced, but I'll only be touching on one good and bad thing about this type of style, since they do relate to anime of the season.
Character Development
Seeing a character react to two polar opposite situations can really make for a greatly fleshed out character, making it easier too seem like they are believable.
On example of this is Sakurasou No Pet Na Kanojo, the male protagonist, Sorata Kanda, is the most developed of the bunch, which ironically is in opposition to what I was arguing in one of my posts. You see Sorata in a variety of lights, from a more comedic end dealing with Shiina, to the deeper end of him trying to figure out what he is talented at and how to accomplish the goals stemming from his discovered talent.
Another example being the newer episodes of Chuunibyou demo Koi ga Shitai!, where we finally see Takanashi Rikka in a different prospective from her high energy, highly imaginative self. I wasn't that interested in Rikka as a character until I finally saw why she was so deeply into her chuunibyou, and know she is far more compelling now.
Lose Interest
That feeling of a series being dragged on for too long, or in this case the slice-of-life section being too mediocre. It leads to a good percentage of people not wanted to continue the series based on the lack of direction or nothing interesting happening.
That was one of my complains for Little Busters!, I dropped it three episodes in on the basis of the characters weren't interesting at all, and the way it was going didn't grab my attention one bit. Later on I did hear that on episode five it got more serious with the focus on one of the females that I probably didn't care for in the first place.
Waiting too long to switch gear does cause people to stall in returning to the anime. I know for me I didn't want to spend another 40 or so minutes watching Little Busters!, just to get to the some what relevant part to a series I deemed irrelevant, in the last hour of watching it.
Conclusion
Balancing these two factor can be difficult to do, which is why more anime companies don't start with a marginally worst section as the introduction to the series. However, I do think these kinds of anime become much better if you like the characters from the start, making their development way more enjoyable of a ride than characters that you never really like anyway.