I've used this feature on the City's website for the past couple of months since it was made possible. Once you're registered, you can track the amount of your bill over time, payment history, and other information - all without having to bother the surly folks at Lake Worth utility customer service.
I do have a small complaint. You are able to store debit/credit card information for use in the future - but even if you do that you must still enter the type of card, expiration date, your name and billing address - even though your credit card number is retained. You also have to re-enter your account number - something not memorized - each time if not prompted by your own browser.
I guess if this was our only problem, we would indeed be living in paradise. But, I do appreciate the convenience of on-line payment - even if it's not perfect.