Although I was fairly compensated for my experience and in comparison to most of the market in my area, pay is definitely an issue for some corporate positions as well as quite a few of the field markets. In the corporate side where there is a lack in pay, in many cases is definitely made up by a great culture, so it will really depend on whether you are driven by money or work environment.
There are quite a few areas of the organization that are understaffed both in the field and corporate based on the workload, but mostly in the field. Many field managers will make the complaint that they do not have time to help, coach and mentor the people and many of the people will complain that they are not helped, coached or mentored. So it is easy to see there is some disparity there which reflects in many of the glassdoor reviews. It is not like this throughout the organization, but rather in pockets.
Career growth can be difficult at times not because they do not want to promote from within, but because there is a lot of tenure. A lot of people love it there so they do not leave. It is also EXTREMELY competitive. There are a lot of very intelligent and talented people in the organization and you have to really step your game up if you are going to progress.
It is a very large organization so the amazing culture you see in some areas is not always seen in others, but I think this is normal with any large-scale organization.