Pros
Big company so may different roles, great benefits including great pension and shares matching schemes. Lots of great people on the ground floor.
Cons
What ever they say, you are just a number, a head count. No one is ever safe from redundancy or (sometimes worse) "talent moved" into a role you don't want to do or is created just to get you out of the way because its easier than sacking you (this seems to happen in management more often then you'd like to think!) The company has grown up very much in silos so even though there are opportunities of all shapes and sizes, your unlikely to get a shot outside of your business unit unless its a pretty ground floor role. The missed opportunity to bring people in from other areas with different views/experience is unreal, this leads to projects required to basically do the same thing, end up running in tandem with double the costs than if the business units just worked closer together.