Pros
Almost everyone at Prime truly believes in doing the right thing and believes in the corporate mission. The benefits are generous and salaries are typically competitive. Internal training is taken very seriously and there are many opportunities for people with the right qualifications. While I was there the way you did your job was evaluated on the same scale as what you accomplished. One of the few large companies I've seen that actually walked their talk.
Cons
Disappointingly, there is a clique of people near the top of the organization who fish, golf and drink together and a lack of women in top executive roles. Also because of the odd business model, Prime is very beholden to the BCBS Associations that own PTI. But those are manageable downsides.