Also looking for it. Is 0.4 the latest stable version? Seems like it goes up to 0.8... (https://gist.githubusercontent.com/HF-SW-Team/224b2a8d746007ec5851/raw/firmware-release.json)

Would you guys recommend to keep 0.2 or move to another version?

That's the file I may be looking for: hashfast-20140224-0-multiarch.tar.gz

EDIT:

There we go for hashfast-20140224-0-multiarch.tar.gz, which allows users to upgrade their Hashfast firmware to version 0.4:

https://www.dropbox.com/s/y43pakhsm7rhr3o/hashfast-20140224-0-multiarch.tar.gz
http://thireus.com/BITCOIN/hashfast-20140224-0-multiarch.tar.gz
https://mega.nz/#!rphhmYpB!X3GPabujIl9EIiZMorVqRY07Z38Ry_HsUw2K44_zDJk

Tested and working on Ubuntu. Big thanks to jddebug for it!