While "Mystery vs. History" didn't get many laughs out of me, I found the episode to at least have interesting subject matter. There's the issue of mystery vs. history--whether Ted should search online for information about his date, whether Lily and Marshall should find out the gender of their baby--and then the idea that the group is very dysfunctional, seen from the outside by Kevin, Robin's boyfriend/former therapist. It was fun to see Ted's dates in the past along with Kevin's diagnosis of the group which included the aside that at least they aren't violent--followed by the violence montage.
One thing that bothered me in the episode is that I still don't find Kevin funny. He's kind of just there, poking in to make comments. Without physical humor or a wacky plot, he hasn't done anything to justify him being there.