Pros
Markel has an extremely long, and consistent record of profitability. Even in soft economic markets, Markel Venture's financial investments have proven to be extremely well-made, and compensate for underwriting losses or overhead costs-- which are consistent concerns industry-wide. The company has an excellent employee-development program which allows for semi-autonomous decision making concerning the direction that employees wish their career to go. The famous "Markel Style" also promotes humility, flexibility, innovation, ethical behavior above as core values. I personally find this a refreshing corporate culture.
Cons
Because the organization is so vast and has a great deal of different business units, cross-training or developing an in-depth knowledge of the organization can be time-consuming. The recent initiative to consolidate and stream-line/centralize many processes has helped to cut overhead costs and improve efficiency, which will improve this.