Asked a dear friend in the finance industry what he thought about Bloomberg. He's the type of guy who uses these systems daily. Mostly paraphrasing:

  1) Bloomberg was lightyears ahead of anything else in the pre-internet days, so there's a lot of UI familiarity.

  2) Bloomberg's chat is important because, as a hedge fund or investment bank, the chat is how you buy and sell bonds. You agree to the trade in the chat, then tell the back office folks to execute the trade. Direct quote: "I'd wager 90% of the ~400 trillion in annual bond trading value happens over Bloomberg DM"

  3) Bloomberg is the biggest and best aggregator

This is fascinating to be because I always assumed latency was the key. After all, the only Bloomberg terminal I've ever seen in person was hooked up to its own dedicated fiber drop. It seems like the chat and sheer breadth of data are the differentiators.