Pros
Being at a large company is beneficial as there are plenty of resources and good talent at this company. It seems that Mercer is really growing despite a terrible market (our new hire counts keep doubling in the 3 years that I've been here). I think as an Actuarial analyst, there is plenty of room to study and they are pretty generous with the study program. Even if you fail out of the program, once you pass a test you are back in the program, and they don't really ask any questions if you decide to reimburse a ton of materials. You get staffed on a lot of projects and a variety of client types, so you should be able to see a lot of interesting situations that you normally wouldn't see in a smaller firm.
Cons
I have read some of the reviews here and a common theme is being overworked. I agree that we are understaffed and even though management says they want us to work normal hours, the office is still quite roudy at 9PM, 10PM, and some even stay past midnight. Of course, I wouldn't mind this if I were paid finance salaries, but we aren't. So what is the incentive? Of course those that do choose to put in those banker hours are the first to get promoted, so what does that say about how management wants us to actually work? One last thing is, I've talked to a few people at Mercer and a few who have left Mercer, and they have all claimed that they felt as though they weren't really using their brains. I find the work here analytical, and sure I can use these analytical skills in other businesses, but when it comes to say, broad accounting or consulting training, I find the transferable skills lacking.