Pros
The people! It is a very diverse, multicultural and multinational environment. You do most of your interaction via video and audio conferences (at least in IT) and you often have no idea which city some of the people on calls are in - could be India, US, Switzerland, China, you name it. You need to grow your network and get your name known for good positive work. This will help you get good feedback and increase your performance review. People listen to anyone with good, strong and sound ideas. Given the size of the organisation, not a lot of emphasis is placed on seniority, and you can quite happily engage with people several bands above and below you. Just learn to treat everyone with dignity and respect, be brilliant at what you do, and you can make a name for yourself!
Cons
You are not likely to get promoted unless you are very junior. The career bands are very protected and you have to be exceptional to get moved from GCB5 to 4, and a god to move from a GCB4 - 3! Bonuses and pay remuneration of late have been quite suppressed, especially if you are a 40% tax payer already. I had no pay rise for 3 years running with a "strong" rating. If you are an average employee (70% of the population), you will get a "strong" rating. "Strong" is just average - thats it. No matter how clever you are or how hard you work, it is very hard to get recognised as "top", unless you are well connected and spend more time influencing than working. I have found this quite unfair, as the people recognised are generally the loudest rather than the best. With interest rates already going up a quarter point and set to rise again, the remuneration and bonus situation could change.