Pros
Significantly more access to executive/senior leadership than comparable FIRE development programs at BoA, Moody's, etc. My coworkers were really great people - many of them knew my kids' names, my spouse's name, my general hobbies, etc. I got to participate in some cool projects, initiatives, fundraisers, and training. Generous 401k contributions vested after 1 year. The underlying nature of their business (capital management) means they do well in uncertain economies and heightened inflation.
Cons
Their transformation strategy is somewhat generic like every other company who overvalues advice from McKinsey and others. Some of the IT /transformation leadership didn't seem to understand IT. Some people have been at Unum for 20-30 years and never had your opportunities as a PDP, so they may not always hide their envy well. There is a proliferation of BS jobs hidden across Unum, and some of your PDP rotations may be one of them. It's not that these rotations are bad jobs necessarily, but you may wonder what value you're adding when you realize your or a coworker's entire step in the process could be skipped with no observable service degradation.