I found this unit to be pretty crazy with the big 5 personality traits, the concept that all of everyone's personalities can be more or less summarized with only five traits. Since I learned about this idea, it's been fun to try and pin numbers onto people. For example, at my work, there are a few people who are routinely late to work--they probably are low in conscientiousness. However, one of them gets yelled at regularly for it and doesn't really protest; whereas the other gets away with it just fine. This could be a fault of my employer, or it could represent the relative agreeableness of the two co-workers. Perhaps the reason one of them doesn't get regularly yelled at is because he has a higher agreeableness than the other (something I would not at all be surprised to see confirmed).
Since these factors are concrete, and have been shown to be relatively consistent across the span of one's life, this idea has also helped me to be more accepting of others, even if they might have some irritating traits. After all, if somebody is pretty much pre-programmed to be low in agreeableness and neuroticism, well, I might not be their best friend, obviously. However, this unit has shown me that there's more to that person than those traits, and what goes on in their heads is completely different than what is going on in mine, so I may as well just accept it and try to get to know that person on a deeper level.