There is a really strong culture of mentorship in the John Hancock Actuarial Program. There is always a student an ASA or an FSA willing to help you learn and give you solid advice. There people here were really understanding of the fact that I came in with little to no experience in insurance, as an actuary or in a desk job and got me up to speed very quickly. By the end of the internship I was helping with requests from other teams investigating why cashflows looked different than expected and making updates to the math model.
John Hancock is a large financial institution with a lot of people. If you are the sort of person who wants a startup feel with flip flops, and knowing everyone in the place you will be sorely disappointed. I personally wouldn't have minded not needing to wear a collar every day but they were very casually about when I arrived as long as I stayed 8 hours each day so I can't really complain.
My managers were excellent.
I was in the Seaport office which is closing so I can't really speak to the office space a new intern would be working in in the back bay. Everyone was always very friendly and nice. Nobody was every high strung which was very nice.