I'm pretty sure being able to continuously observe with such a device how the brain works will speed up research in the field.

Also, whether this is a good thing is very questionable. I expect that in the future these devices will contribute a lot to being able to manipulate any users emitions and thoughts in any way, without them noticing or being able to fight against it. First by giving more insight on a person's way of thinking to data brokers, more efficient targeted advertisements and news can be fed to them, and later by directly manipulating how the brain works.