The impact of the APIs will surely be different depending on the scope the industry settles on – smaller, if we just stick to plain access to account (XS2A) and payments; much larger, if product information and origination is also exposed.
One of the results expected is the golden era of intermediaries and aggregators – services such as Mint.com which cannot wait for the APIs being exposed universally. It would be a convenient thing to manage all accounts from a single app.
But the true potential to be unlocked is different, possibly understood by most, but somehow hardly explored. The true benefit is the dawn of composite, multi-provider products. The banking super-products.