For example (and obviously), all settings related to UMD Video are missing on the PSP Go's firmware. More bizarrely, "Battery Information," which displays how much battery life is remaining, appears to be gone. Additionally, "Backlight Auto-Adjust" seems to be missing from the Power Save Settings menu. We're not entirely sure why these options are gone. Could it simply be because it's an early version of the firmware?
Obviously, some time remains before Sony officially releases the Go and firmware 5.70 to the world. It'll be interesting to see if any of these changes affect the older UMD-equipped versions of the PSP. Considering firmware works slightly differently on each of the 1000, 2000 and 3000 models, we're sure to see differences evolve across the platforms over time.