You know what you're getting, it's a safe place
Pros
It's a 45-hour per week financial services job. When you leave the office, you don't have to think about your job until you get back the next morning. And even then, you could easily get away with calling out or coming in late. If you can find a good few friends in the office, particularly in your group, it makes the job a lot more bearable. An added bonus is you can definitely work this day job to support an entrepreneurial venture of your own. You can also get away with working on your own stuff during down time - which there is a lot of throughout the day. Also good to take advantage of 401K match.
Cons
There are a lot of routines that become mundane over time. General ledger processes aren't very exciting. A lot of times it feels like you're a glorified data entry employee. And you're not even that glorified for it. But again, you know what you're getting at State Street. It's safe.