Complete list of enhancements versus original 1.1.1 firmware (B7 - released June 1, 2004):
Custom function menu found on the last page in the menu
Ability to define how the SET button behaves (same menu found on the 10D - refer to the 10D manual for full explanation of these new enhancements)
Exposure level increments either 1/2 or 1/3-stop
Option to enable 1/200th flash speed sync in AV mode
Ability to change the JPG size when shooting in RAW mode
Shutter release with or without CF card
FEC adjustment via the JUMP button, use the dial to adjust as shown on the LCD
ISO3200 now available, and is represented by an "H" in the LCD - same as how the 10D shows this
Mirror lockup available via enabling the option in the custom function, works by pressing the shutter button which flips the mirror up, then the shutter opens about 1-1.5 seconds after MLU - note that this is different than how it is implemented on the 10D where you press once to flip the mirror and press again to open the shutter
Immediately pressing the ERASE button after taking a photo, you can delete the photo by pressing the ERASE button again instead of selecting Ok previously, to not delete the photo press any other key
Left button changes the focus mode, and is displayed on the LCD as follows:
PA-0 Lens set to manual focus
PA-1 One shot
PA-2 AI-Servo (selectable but cannot take a photo - one workaround, hold the shutter button all the way down then switch the lens to manual focus)
PA-3 AI-Focus (first takes one shot then the camera may switch to AI-servo depending on what you are focussing on)
Right button is for changing something (believe it's metering) but this does not do anything - so ignore (values if you're curious are PA-0, PA-1 and PA-2)
Watchouts:
camera may lock up if you attempt to change the language
some features may not work correctly if you are using another language - use English as a workaround
if you upgrade and some of the things don't seem to work properly, set the settings in the Custom Function back to the original values (see below) and install the original 1.1.1 firmware, then upgrade to the new firmware
change the SET button to something other than FEC before upgrading to this version