There is an inadequate amout of people to get all the work done as best as it could, so people that want to be rated highly often need to put in a lot of extra time and effort. Also, some departments are more together than others-- end up working for the wrong department (like custom, for instance) and you could nearly lose your mind.
There also seem to be some areas of the company that aren't able to be as innovative as we need to be in order to become a leading EDUCATIONAL (not just publishing) company. I think another downside of Pearson is that there isn't very much time for fun anymore; you don't see groups getting together for drinks after work (something I did at previous jobs) or even getting together for lunch often.