Pros
They have competitive entry-level benefits and compensation (great 401K match). Additionally, you are taking part in a company who has established thousands of relationships with employers, credit unions, and alumni groups which allow you to tap into semi-"warm" leads. Unlike most other positions among P&C insurance, the overhead at Liberty Mutual is taken care of.
Kontras
In the beginning stages of the job, you have to weather many mundane computer modules before you are able to start making any money above the base salary. Another downside is once you get your business going years after starting, you have to work very hard to keep up what you were able to make before the base salary trickled off. There is also the other downside of not being able to get a large return on renewals compared to other companies. The emphasis is placed on new business much more than maintaining current business.