not if you add it to your existing account you dont though. If you log into your existing account, go to manage keys and add it in there, you will gain anything special (say in the special edition you get the free unlocks) but you will NOT get extra character slots. Kind of a waste.
However, if instead of clicking log in, you choose "New Account", you can put in a different email and password and put your new key in there. You'll have to unlock all skills/upgrades again but you will get the four extra slots. Also the accounts are linked in no way so you need to either have 2 pcs to trade to yourself, or have a very good friend you can trust if you want to move items around
