Pros
Fidelity has a very competitive benefits package, and good opportunities for training and extending your knowlege of financial services. There are lots of opportunities for working in different departments during your career. The average tenure of Fidelity employees is quite long - something like 10+ years, so you could build a long career here if you want to.
Cons
Management is out of touch with market direction and needs, and technology personnel are viewed as "overhead" or an "expense" and not really an investment in the future. There is a tremendous amount of bureacracy and layers of removal between the customer and the people actually doing the work. Having "fun" at work isn't really a priority, eveyrone walks around with their head down hardly cracking a smile most of the time. It's all business, all the time, but a lot of efforts being duplicated and /or wasted.