Sometimes it's best to take a gap year if you really aren't sure about what to do with your life...even though it dosent seem it at the time, your loan is your money, and to spend that much money on something it helps to be sure about it. A gap year can give you the time to just think about what you really want.
I know some people who just took very simple gap years earning money in very basic jobs...they didnt want to have to borrow as much, or they wanted the funds to go travelling.
On the other hand I know people who decided to spend their gap year getting relevant experience for their career, even if it was very poorly paid. I think it depends how clear your plan is of what you want to do long term.
hope this helps (I didnt take a gap year, but I looked into it a lot. I realised the reason I wanted to take one was that I didnt want to leave my friends, but they were all leaving anyway, so it would have been a bit daft!)