I received an email offer of a 5% discount off my fare (not just OBC) if I paid my remaining balance in full. However, when I called to redeem the offer, they only applied a discount of around 2.5-3.0% of my full fare. I emailed customer support, didn't get a response in time, and ended up redeeming the offer anyway just before the promotion window expired. Not a very pleasant experience.
In hindsight, I really regret taking advantage of this discount. I could've put the dollar equivalent of my remaining balance in a savings account and received much more in interest than I saved on the fare.