I had to learn many actuarial and accounting concepts in order to do my work. To further the life versus casualty discussion in response to Seth Anderson's original question, I offer a few generalizations of some of the differences. First off, I am 5 years out of a university degree in Actuarial Science. I am an ACAS, and an ASA, who experienced both sides during university work terms and consciously chose the casualty side at graduation. This makes the casualty side require more statistical analysis, but means the numbers on the life side have more statistical credibility.
Disability insurance is to some extent a middle ground.
The life insurance side is currently more into investments. Life is longer term after all, but this is changing, and the casualty side is working on the investment side. Many people view this as big growth for actuarial, and view the life side as being more prepared. The casualty side is newer, and less developed. This might be more true in Canada than the U.S., but on the job itself, I found on the life side I was doing more running of somebody else's program, or system, and on the casualty side I was doing more creating of my own.