I like this old rule of thumb: don’t borrow more than your first year, post-grad salary.
For most GSers, that leaves consulting and finance. If you don’t want to go into one of those fields for at least 5 years you will have a tough time servicing your debt.
After nearly a decade in finance, I’m now shifting towards becoming an entrepreneur and, oddly enough, nobody cares that I went to Columbia (or went to college at all).