AFAIK, the only differences were the mounts that were supplied with the unit were revised to suit newer mac models.
Obviously, the firmware that shipped with newer models would have been updated at the factory and rev A iSights have a
download-able firmware update.
I also recall that the plastics used in the rev C were "environmentally safer".
Actually M8817LL/C includes the magnetic mount, whereas the M9330LL/C doesn't.
The final model appears to have been the M8817LL/C
Until the M8817LL/C there were 3 mounts. It seems the M8817LL/C ADDED the magnetic mount.
EDIT: too late.