I like that you can view your salary history (and promotions) in order to see what raises/bonuses you have received over time! It's also great for tracking annual performance reviews or just keeping track of how much money was spent during previous years at my current employer vs where it could be allocated into other departments within our organization.
Having all this data has allowed me personally as well as management team members alike better understanding compensation trends across different positions throughout several companies - which helps when making decisions regarding salaries moving forward. Not really any downsides that come with having access to these numbers but being able to easily compare pay between 2 organizations would definitely help if there were such concerns. Currently looking through historical information to prepare myself for future career moves so am not currently using functionality provided here; however, once used they are helpful because employers tend to keep records going back more than 5yrs from most recent employment.