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Hi, I've just recently discovered a bug that will be fixed in the next update.

Please try to limit the amount of concurrent connections to 1 (default is 3) in the FTP configuration screen. There's currently a bug that results in a crash when directory listings are parsed in several concurrent threads.
Samba seems to be licensed under the GPL. This doesn't allow me to use it in an iOS app. I'm not aware of another SMB implementation under a BSD or similar license.
You are right. It's currently not in the docs. I'll add it.
I just answered because you wrote it as a question :)

If I added this, I would have to support many more clients than just FileZilla. For example popular applications like Transmit, Dreamweaver, CyberDuck. I don't have plans to add this in the near future, sorry.
Currently, you need to manually enter your FTP account details. 
Did you see that you can get a list of recent files by tapping on the current file name? 

This is really meant as a kind of replacement for tabs which would take away screen real estate.
Can you please send me a crash report? See http://feedback.textasticapp.com/topic/48133-how-do-i-send-crash-reports/

Are you absolutely sure you are using version 3.1? I tested it with much larger directories on Dropbox and it didn't crash for me.
Is this with Dropbox or WebDAV or with FTP downloads?

Just a few hours ago I discovered a new bug with FTP downloads. Please try to limit the number of concurrent connections to 1 in the FTP configuration screen and try to download again.

The bug happens when parsing file listings from the FTP server in concurrent threads. 

Let me know if that makes any difference for you.
I could reproduce the problem now. It will be fixed in the next update.