Pros
The scale of projects can be enormous, which can be a cool challenge. Travelling abroad, getting to know different industries, there is a lot to discover. Also, there are a lot of nice people in the company, but you will have to filter them out.
Cons
Almost every internal process is broken in some way, from everything related to HR to reporting to IT. And the massive scale means everything is generalized so outliers, for example if you have a less common function, role or skill profile, run into problems all the time. Computer says no, usually, and most managers do too as they are used to this generalization and don’t want to deviate with anything. On top of that, project success is measured by the number of escalations. Think about that: the positive scale doesn’t even exist, the benchmark is to try and minimize the negative.