Big,
generally the system dump is most helpful initially for other phones. It allows folks to pull wallpapers, ring tones, graphics etc. to try on other phone.
I guess apps would be next, again to let folks try the "new" things on other phones. Eventually the aps get pulled apart potentially for use on this phone, as modifications or eventually to theme etc.
At the development level, the developers share these dumps from all of the phones that get released as a way to try and pick and choose what can be modded, sometimes to fix something broken on another phone, perhaps grab a library or OS file that can help get a developer over a hump on another device. A good example might be to snag audio files or drivers to help make the FM radio work on another device for which the necessary files may be missing, but the hardware is in place. The fm is not specific to the D3, just an example that has been done in the past.
Generally the sharing of these files across all devices allows developers a way to pick and choose through the files to see if they can get help, or make mods, for this phone or other phones.
Craig