Pros
Celanese is a tough culture but it rewards those willing to put the time and effort in. The company wants to be the best in everything it does, and you can't help but be inspired by that. Senior leadership is very strong and they measure everything so you understand how you're doing against the competition. It's a global company and you'll learn a lot about doing business in other cultures. They compensate very well for top performers.
Cons
It's not for everyone. Work-life balance is something they admit they don't pay much attention to. You need a thick skin to work there (or you'll develop one quickly). It's essentially an up-or-out place. The top performers get promoted and well-compensated. The lower performers (who might still be valuable in the right circumstances) usually are let go.