Pros
MassMutual has one of the best benefits package in the Fortune 100 group. Tuition reimbursement is upto $8500 if you are in an accelerated degree program, or $5000 otherwise. There is no management or HR approval needed for undertaking any study. The pay is also above-average in most job categories. Being a mutual company, they are rather stable and do not indulge in haphazard reorgs. The work culture varies by the functional area, but if you are in IT expect to work long hours. The place if full of people who have worked here for 20-30 years and if you are even just mediocre, you can easily survive here if you don't piss off the people who matter.
Cons
This place is a complete bureaucratic mad house. There is red tape everywhere you go and the culture is ultra-conservative. Watch every word that you speak in the first few years as things get political very easily. There are strong cliques of workers who have been around for more years than you may have lived and most of them are just lazy parasites who collect their paychecks every two weeks and are waiting for retirement day. The opportunities for career advancement are slim to none unless ingratiation is a part of your skillset and you can handle the disgust of brown-nosing the big cheese everyday. Not saying this with any prejudice, but if you are Irish Catholic, you will do well very well here. If you a person of color or a foreigner, expect the looks though on the face people will be polite.