Different programming languages have different established coding styles. Ruby is intended with 2 spaces, Python with 4 spaces, Go with tabs. 

At the moment, Textastic only supports one global setting for indentation. File-type specific settings would be useful.

Would it be possible for auto complete to work with variables and functions within the file you are working on? This would make coding a lot quicker as previously used functions/variables would be a part of the auto complete list.

I prefer to use batch edits with multiple selections feature like sublimetext 2.

Curious as to whether you've considered creating a API that would allow others to write plugins for Textastic - that would allow some of the functionality requested here to written by others, so that you don't have to do all the work :)

Would be great to see "Move Line Up / Move Line Down / Comment Selection" text transformations ala Xcode's Editor->Structure menu. Thanks!

Open two files side-by-side and compare (highlight)

It would be nice to have Goto Offset/Position (character) option so you can navigate to the character/position in the file with specified offset. It might be rolled into one Goto dialog with goto line like 100 is line number, 100:10 is relative position 10 on line 100, and :1234 is the absolute position in the file (character based).

I would like to see a preference so I can render markdown (I use Multimarkdown mostly) in a user selectable app.  I use Marked. 

as it is, the type is too close together to be pleasing.