As kind reader has notified me Canon recently released another EOS Digital Rebel XTi / EOS 400D Digital Firmware Update.
Firmware specification changes
This firmware update (Version 1.1.1) incorporates the following fixes and improvements.
- Adds detailed information about three new lenses.
- Polish has been added as a new display language in the menu screens.
The Version 1.1.1 firmware being released this time is for cameras with firmware up to Version 1.1.0. If the camera's firmware is already Version 1.1.1, it is not necessary to update the firmware.

As really well put in this dpreview forum thread, there is nothing new that average owner will ever notice, unless Canon sneaks some fixed without stating that in what's new.
As usual, I'll update my firmware. And if I don't post anything about it again, it just means everything went ok. ;)