Vantaggi
BP does reward individual performance and is an ethical company. You won't be asked to do anything that is unethical or illegal, and if you are they do a good job of making sure those people aren't allowed to continue working for BP. There is plenty of opportunity at BP if you are willing to work for it. They have good benefits and try to help employees maintain a healthy work/life balance. Lots and lots of good people there.
Svantaggi
If you aren't an engineer or a person with a science degree, you will have a hard time finding a career path that is clearly laid out for you. If you aren't an engineer, be prepared to hit a glass ceiling and be prepared to wait much longer for a promotion. It is a company of engineers who promote and look out for other engineers. The glass ceiling is real and is nearly impossible to break through. BP puts too much faith in engineers and somehow equates the ability to do math with leadership ability.