Pros
Essentially an engineering company Job for life, if you behave yourself. Good to have on your CV (probably) Financially stable employer (and, even if company "went to the wall", you would still have a job as it operates in a natural monopoly) Big group of older-end employees will retire in the next decade leading to lots of opportunities for young 'uns
Cons
Over last last two decades there has been a relentless drive down on pay and pensions (which, from an engineering recruitment/retention point of view, has probably gone a bit too far) Can be difficult to move into some parts of the business, e.g. operations side, unless you started as a trainee/apprentice in same Very hidebound with rules/procedures (but isn't every big company/institution these days?)