Vantaggi
With the company being so large, it is relatively easy to gain rapid promotions. HQ location is easily accessible, and most of the employees are great people. The owner, Charles Koch, will send you a Christmas card every year (no bonus enclosed, sorry).
Svantaggi
If you do too good of a job, you'll be told you cannot apply for another internal position. If you don't get a promotion, you won't get a raise (despite them raising the salaries for new hires!!!). In general, by the time you are eligible for a promotion, they just give you more work, but only the same salary that new hires in your former position will be paid. Don't expect a performance review. You will have to complete a self review, as well as many peer reviews, but you won't see the result of them from your supervisor. They always tell you "we'll have it next week" but you never will. I didn't receive one for the last 2.5 years I was with the company despite repeated promises that all managers are required to give them annually. It doesn't really matter though since you won't receive a raise. Nothing better than being told that the company is having record profits, that your performance "exceeds expectations" and then being told that they cannot afford to give you a raise.