What I did was force myself to learn vim. Nearly all of my stuff is web development of some sort and runs on a Linux server (usually Debian). Vim is available on just about every platform so by learning it I can code "anywhere."
What I do is use Panic's Prompt app to SSH into a production or development server and code there (remotely). I use git to checkout and commit my work and (GNU) screen to keep my sessions going when iOS inevitably quits Prompt while I'm researching something in another app. GNU screen is also nice because I can divide my window up, have multiple tabs, etc. so I can really get a lot of things going on the server and switch between client devices (laptop, iPad, etc.) while preserving my work station (so to speak).
e: I should add that I've tried Coda and Textastic, etc. but in the end found that just coding remotely with vim to be an easier environment since I didn't have to worry about uploading files after making changes. With vim the file is already on the server and I can just :w to save it, then test the results.