If you don't like the sound of Accenture and CGEY, I'm not sure IBM is for you. You will spend most of your time out at client sites so the atmosphere will depend on the project team. Your work/life balance again depends on the project: you may be on a 9-6 job you can commute to, or you may be on a long-hours project based in the back of beyond. You do have some say in which projects you do, but you also have a responsibility to keep your utilisation (hours billed/hours available) high.
For getting a broad range of consulting experience, then joining one of the big companies is great. On the down side, IBM has been nicknamed the "Interminable Bureaucracy Machine" more than once.