Pluspunten
There are many opportunities for moving to other departments, as they are typically willing to train the right person. This gives you the ability to get many different experiences within the company and not get stagnant. The benefits package is above average with a nice pension plan for employees and agents, although I've heard that newer employees are no longer being offered the pension (something to look into). State Farm provides a lot of support for continuing education and professional development...even reimbursing for tuition and paying for insurance designation programs.
Minpunten
Unfortunately, you must be willing to relocate in order to move up the ladder. Most of the employees working in the departments that support agents have no concept of what it's like to work in the agent's office. State Farm tries very hard to be all things to all people rather than sticking with what they are good at (insurance) and working with a few target markets. Because they want to sell insurance products, bank products, and mutual funds, to almost every conceivable audience out there (youth market, retirement couples, hispanic market, asian market, african american market, small business owners, etc, etc,) the resources within State Farm are diluted, reducing effectiveness in any one area, and the agent's office is completely overwhelmed with competing priorities. Don't even think about trying the agency opportunity unless you already have a background in insurance and financial services because they are not going to give you the time you need to learn and develop as a salesperson in the first year. The quotas are so high, especially for life insurance and bank products, that if you don't have a background in the industry, or are able to hire an extremely competent team (which is usually impossible given a small business owner's payroll and the available talent pool in most markets) they will make you miserable in the first year so that you want to quit even if they do offer you the contract.