Most banks uses this system. I used on a daily basis. However, it is kind of clumsy to enter trades on. I'd say the main value it brings is the readiness of all types of data. That is, _ALL_ types of data that you want to access is within a few key strokes. Their UI isn't too pretty, however the speed is awesome. I heard that they have 1 CPU dedicated for each client connection.
-eraci-