Pros
I was in the R&D department of Bloomberg for over 10 years. The company is very profitable therefore job stability, health benefits, time off are all very good. The company controls their own technology stack from the client software running on the user's desktop, to their network connection end to end, to huge data stores in their data centers. As an engineer, there are many interesting problems to work on. However, due to the profitability of the company, there is not much incentive to do basic improvements to their infrastructure, reduce operational costs, or increase automation. This can be frustrating as much of the organization is involved in updating work tickets and doing manual changes. This kind of environment can be great for someone who wants to not think or work too hard and just punch in the clock.. but if you are intellectually curious and are ambitious to learn new technology it can be very suffocating. Further, much of the organization is involved in operational roles and have no desire or passion to improve technology.
Cons
I would recommend this company for someone starting off out of college or for someone who is very senior looking to get a great pay package and looking to relax for their remaining work years. For engineers who have been in the workforce for more than five years, it is a very bad proposition to stay at Bloomberg for too long. The compensation increases eventually are very incremental and are below market compared to other technology companies that offer equity. Further, the lack of innovation and improving technology can slowly destroy your competitive advantage against your peers.