I travel into London once or twice a week, so have to pay for single days rather than a week or month at a time. The current website is appalling. For a start it is always having problems - I had to spend all of Monday trying to pay online, and it's half-term so it shouldn't exactly be overloaded! In the end I gave in and phoned them up. Even when you do manage to use it, it has obviously been cobbled together from all sorts of bits and pieces.
I hope IBM will produce a much better website. Having it automatically debit your card is something I have long wanted. It would be very simple to add, but Crapita won't do it because otherwise they wouldn't be able to fine so many people who forget!
Unfortunately the congestion tax is just another example of a system where there is no onus on the provider to give good customer service. The public have no choice but to pay it so why bother making it easy?