Does using this simply increase the bounty you get for killing wanted crims? Any other advantages i.e extra rep etc?
As mentioned above...
It increases the bounty by allowing you to gain vouchers for bounties that the ship/pilot has in all factions in the galaxy.
Whenever you cash in bounty vouchers you will gain some rep with that faction/allegiance that the bounties relate to.
If you are in a reasonably calm nav beacon or RES you could scan a ship with standard ship scanner and check in the contacts screen (left interface) to see what the bounty value is and then KWS the same ship and check the value again, you will see if there is increase in value.
Larger and/or more dangerous wanted NPC's will have greater bounties and also a greater increase when scanned with a KWS.
It won't be long until your mouth starts watering at the prospect of a 140k+ bounty from a 'conda thanks to the KWS.
