I used it a bit back in college to avoid overdrafts. When living with no income and under 1k in the bank, it was pretty useful.

It would predict automatic payments, and allow you to take out a small loan to cover the payment, avoiding about $35 in overdraft fees. And the best part was the payment back was 0% interest, only you couldn't use the service again until you paid Dave back.

I'm sure they got their money's worth from banking data after I left it signed in for 5 years. Eventually I deleted my account and unlinked my bank.