SSL libraries never have bugs.
Its a great idea if it could be done without giving you any of my bank credentials beyond what is on a check and basically public knowledge.
https://plaid.com/docs/#add-user
That right there is why I won't use it regardless. No offense to you or Plaid's security. Just the idea I'm going to hand over the same credentials that let me transfer money out of my institution isn't an acceptable solution.
Your account and routing number are all that's needed to move money in or out of your account. SSSavings does not get these, nor should any application you don't want to debit you. Unfortunately, these numbers cannot be changed without shutting down the account (whereas credentials can be changed quickly).
Same with routing numbers, though finding the routing number of a Bank of America account opened in CA, for instance, is just one google search away.
That said, I'm stoked about checking out Plaid sometime soon especially after reading the Yodlee docs (yikes!)