Disclaimer: I'm part of the combined TfL and BAE Systems Applied Intelligence team (née Detica) that did the build and architecture, along with the great folks at We Are Experience and Attenda.
Another minor quibble - print the rules for passwords before people submit an invalid one. And if you do force a resubmit, persist all the form settings or you're going to annoy me^Wpeople.
Very happy to see that TFL have done as much as they have though. Lovely to see :)
Edit: ha, beat me to it alex :)
(I'm part of we are experience)
Having a fully responsive version means that users will navigate the site on mobile devices where data networks are not always good.
Do you intend to reduce the JavaScript payload?