I think about the following use cases:
- 'Perfectly' reverse encryption without loosing settings
- Update ROMs. Even if /system, /data, /sdcard (internal) are encrypted
- Low level Backups with CWM. When SDCARD partition is also encrypted.
- Emergency access to my data (screen broken, soft bricked...)
- How to mount crypted dumps on linux (knowing the passphrase)
Is there some salt value going into the key together with the passphrase stored on the device?
I currently use a tmpfs mount to /sdcard and 'adb push update.zip' on my Nexus S to update the ROM. I've been told that the Galaxy Nexus also has an encrypted /system which would prevent all that (see Nexus S solution here: Broken screen, can't adb )