I'm a little skeptical about the whole thing. I paid off student loans... and it sucked. But it was up to me to balance the risk vs. rewards. I like easing the student loan burden, but I don't like the idea of subsidizing some kids decision to get a masters in english lit only to complain that he/she can't afford to repay that on an English teacher's salary. There has to be a balance somewhere. Equal parts "yes Johnny, we will cap your student loan repayment" and "no Johnny, you won't make $90k/year to repay the loan for a masters in the history flip book animation". I don't know how to implement that balance.
Talking long term about balance is good, as it has been pointed out recently that psychology and communications majors outnumber engineering majors. This isn't really sustainable, and going forward having categories of loans for different majors is something to consider. However, for the current proposal, the President isn't talking about education policy; he's talking about fiscal stimulus. Therefore, it is merely punitive if we start saying that Person X should get favorable loan terms by virtue of their computer science advanced degree, while Person Y does not, because they hold a bachelor of arts in the humanities.