There are pros and cons to having an agent after art college, its an idea I have been strongly contemplating with.
Some of the pros:
They can get you out of the "Slush" Pile
Better advances and contracts
More professional at selling work
They know all the legal lingo
Bring you more work
They take a fair amount of commission
Doing it yourself with help build your confidence
Agents represent more than just you.
Moneywise is it worth it?
Taking all of this into consideration I feel it will be more beneficial especially when you are first starting out to have an agent. Its a smart move as they will hopefully be able to put you out there more than you could when doing it on your own, as they have the contacts. As I have discussed before in todays society it is more about who you know rather than what you know...