It sounds great, but I'm always left wondering what the angle is for free services. Will they make their money off of float? Is it something to do with the way debit cards are charged?
I think linking accounts to debit cards is pretty valuable on it's own. It opens the door to making payments for a lot of people much easier down the road.
Like how Paypal encourages you to tie your bank account to your Paypal account; they get to charge merchants the credit card interchange rate while taking advantage of the low ACH funding risk on the buyer/purchaser side.