Amazon refuses to publish what changes have been made in every firmware updatde. It is annoying because sometime some useful features disappear in an update. This is the wiki page to reflect the good/bad changes with each update right from v4.0.0. I hope it help people to decide which firmware is best suited for them based on major/minor changes.
 Kindle Touch Changelog
In each section, there would be two parts, one names + and the other -, former is good changes and - is bad changes!
 Update 4.0.0
This is the first version... Welcome to K4 buddies. :)
 Update 4.0.1
+ sshd present in diags partition + root password is 'mario'
 Update 4.1.0
- Removes sshd from diags partition forbidding ssh acces via USBNet in diagnostic mode.
 Update 4.1.1
+ Re-added sshd to diags partition (root access can be gained using USBNet in diagnostic mode, ssh to firstname.lastname@example.org)
- Root password must be generated using serial number (looks like fionaxx00)
#!/usr/bin/env python import hashlib print("fiona%s"%hashlib.md5("XXXYOURSERIALXXX\n".encode('utf-8')).hexdigest()[7:11])
 Update 4.1.2
 Update 4.1.3