Pros
Unum does a lot of internal hiring and promoting. If you get in and do your job and work hard it is unlikely you will stay in the same position. They will encourage growth. The pay is also fairly competitive. They have some great benefits as well. After the first year they will give 4.5% toward your 401k and match if you do 5%. They also have an espp program which allows you to allocate up to a certain amount of pay towards buying stock at a 10% discount. I think I would also add their training (at least in my area) was quite robust. I feel my expectations are very reasonable and well rewarded.
Cons
Honestly there are not too many at this point for me. It is certainly a job so there's that. But I know several people who have received salary adjustments because they felt the market had shifted and moved salaries to be more competitive. My former employer did not ever give raises unless you fought for it. One complaint I do have is that it feels at times the company pushes inclusivity to the alienation of anyone not socially or politically liberal. I am fairly new I have already felt a sense that inclusion does not include social or political conservatives. I know of many coworkers that feel uneasy even sharing they are Republican for fear that it would damage their opportunities for mobility in the company (which given our headquarters are in Chattanooga TN that's really odd).