Your comments

The cursor position (selected range) is now saved - even between app launches.

Will be available in the next release.
This is now fixed for the next version. Username and passwort are now saved securely in the keychain.
Hrmm, that's odd, in my tests I copied much bigger text without problems (a few thousand lines). Which iOS version is this?

But, I already fixed a crash that would happen when you are at the very end of the file and choose "Select" in the context menu. This will be fixed in the next update.
How large was the text you tried to copy? Can you give me an estimate on the number of characters or lines?

I assume you ran into a memory limit with the undo manager. Currently I don't check the text size when doing copy/paste.
Should I completely remove the sidebar and only use a popover like it is implemented in portrait orientation or should it be an option in settings?

The sidebar is good if you want to quickly switch between files (for example when viewing a larger project and not editing it).
Thanks for pointing that out, Erik. I have updated the text. I didn't know that the Dropbox app caches the directory structure and recently opened files.
Hrmm, I just discovered "Snipplr" at http://snipplr.com/

Could be cool to add support for their "social code snippets". They have snippets for all sorts of languages.
Well, with multi-tasking in 4.2, Safari is only a three taps away. So I would only implement a local preview.

Otherwise I would have to raise the rating to 17+ because it would be a browser...
It now correctly says "Do you want to open this link in Safari?"
Thanks a lot for the detailed description! It is certainly a very good idea to offer some predefined key sets and allow to people to create their own.