Yes and no, in some way, taking student finance is like a gamble. At the end of uni, you may get a career that will take you over threshold for paying back or you won't. If you don't get over the threshold, then you'll never pay it back (mine is written off after 30 years I think), and if you funded it through other means, then you'd technically have paid more than you needed to.
If you do get over threshold, it's then a matter of whether you'd pay off the full amount before the write off point. If you're earning above the threshold but won't pay off the initial sum, then the interest amount is by the by.
The issue with the interest is if you're set to pay of the full amount before its written off, and therefore will have more to pay overall.
Higher earning parents/families in some ways are at an advantage, in that they can avoid the high interest rate and wage deductions for life, if paid in advance. The interesting statistic would be if such families are more likely to get a career after uni that would set them to pay the full amount off.
The people most at a disadvantage are those without means to pay outright for their tuition but are on track to earn enough in their life to pay the full amount including interest. But that's not realised until after graduation.
It's a really significant change, but it's hard to determine how many people it would actually affect in real terms.
Currently I earn below the threshold, and as the threshold rises each year, its unlikely I'll ever pay off even the initial amount, so the interest amount doesn't really mean much to me at the moment. But as I have no way to predict my future earnings, it could impact quite heavily later.