"The Break Up" isn't that funny, although it has its moments, especially when Brooke's brother is onscreen, an acapella martial artist who "isn't" secretly gay (hehe). But overall it didn't pull many laughs, and it was slightly depressing in parts, but intentionally so.
I guess it's a problem when you don't want the two main characters to get back together. This is assuming the audience is meant to root for them, and why wouldn't we be meant to root for them? As it is, Vince Vaughn's character is a jerk who doesn't deserve the caring girlfriend who dumped him, who cries over him and wants to get back together (unbeknownst to him). Luckily, this movie doesn't gloss over that fact. It's a big part of the story, of the point of the story. It's not about getting back together while doing silly things (which, uh, they do), it's about a relationship gone to hell, about why it went to hell.
Jeez, I just made it sound somewhat deep, which I shouldn't have done. I mean it makes its point, but it still isn't that good.
But here's a pro: I appreciate how it didn't end in the totally cliche way that I expected it to.
My grade: C+