This post is from a user's perspective rather than a provider's perspective. I use both my bank's bill payment service and I have enrolled in a variety of merchant direct bill payment programs. I use the bank approach mostly for the gardner, dentist, etc. I use the merchant approach for my wireless, water, gas&electric, etc.
It surprises me that there is so much inconsistency in the way the "biller direct" models work. I have also signed up for paperless statementing from most of my providers. Regardless of how I get notified that a bill is pending, some statements include the dollar amount and the date that the payment will be processed and others make you log-in to get one or both of those pieces of information.
I am sure that some very smart and well meaning programmers/product managers had good reasons for their individual approach to this, perhaps security concerns about email exposures, and/or the information they needed to populate the fields was not easily available.
It would seem to me that some studying of the Best practices in this area could help to further the adoption of these great programs since consistency is key to massive adoption and reduced costs for customer service.
I personally prefer that I be reminded of three key pieces; How Much, When, What Account (Credit Card or Checking) is going to be hit without me having to log in and probe for that info.