I had experience with Capital One I think, their connection flow was horrible and broke the UI of your app: Basically your user had to go into a Capital One webpage (which was pretty ugly, specially in mobile) and then there were several checkboxes that they had to click through to allow specific accounts to be "seen" by the Plaid like services. Then they took you back to your application and if the user selected not to share any account, your application would basically crash.

I cannot imagine the UI hell that Plaid will be when every bank implements their own propriertary flow for approving account visilibility.