Your comments

Thanks for answering this. Works well. 
I second the idea. My use case is also developing apps in HTML 5 for ipad.
I'm currently using G***o for coding on my iPhone as it's the only real option for iPhone. Textastic on iPhone would be awesome - even as a separate app. 

Another use-case, atleast for me, is being able to get ideas down in code when they come to me when I'm out and about.
I second the idea. Taping the line number to place a bookmark is a good idea and would really help with navigating long files of code.
I'm in the same boat. It's great to have a nice editor to code in but without being able to run my php code it makes things difficult.