Since your code completion update, Textastic has become, by far, the best IDE one can by on any mobile platform, nearly as good as desktop IDEs like Aptana. Full firebug debugging, basically tabbed document browsing, really well implemented code completion, really well thought through keyboard manipulation and touch interface. Preview function, but also remote preview so you can even edit and debug php apps and such on a remote server.
I've literally tried ALL iOS code editing apps and ALL Android code editing apps, spending literally over $100 on code editing apps looking for something that is even remotely equal to a desktop experience and nothing even remotely approaches a desktop experience, except Textastic.
I find I can literally sit at my arm chair and develop and debug full html5, web apps, both front end with html5, css3, js (all with firebug debugging, off line or online) and server side with php (maybe even firePHP could be implemented?).
Truly an amazing product well worth the money.
Customer support service by UserEcho