I used to use Chase's online bill payment (via Quicken) and liked it up until a few years ago. Originally, I'd pay a bill and, when necessary, a check would be printed and mailed. For clueful payees, the whole transaction would be paperless. Cash never left my bank account until the check cleared. Then Chase changed things around. Now, they take the money out of your account in advance, whether or not the payee ever receives the check. That means, if you're paying your credit card bill, you're basically giving the bank several days of additional "float" on your money with zero interest. In one case, where I paid a bill that required a check to be printed, to my gardener, he never got it but the money was absent from my account. Cleaning that up was annoying.

I've since switched to Fidelity's BillPay. It's all online, through their web site, and free of any fees (minimum balance requirements, etc.). This works how you would expect. The money is in your account, earning you interest, up to the minute that the payment clears. BillPay also knows how to present you with your bills (either showing you HTML inline, with some vendors, or linking you out to a vendor's web site, for others), email you when a new bill has arrived, etc. It's about as painless as you could possibly want. About the only problem I've found is that it doesn't load properly on an iPhone. Yet. They're clearly working on an iPhone-specific front-end for Fidelity. It works in parts and fails in other parts.