I have lux installed. Many times in doors or at night even 0% is too bright for me, so I set lux to - 25 or - 50. In the daytime in my car or outdoors I set phone to 100%.
I use Lux. SGS3 Auto Brightness is FAR too high brightness even at night. The lowest available brightness setting is still overly bright. Lux takes care of this and drops the brightness even lower using dimming filters. You can even customize your own Auto Brightness settings instead of being stuck with SGS3's default Auto Brightness.
Mine is usually either full dim or full bright. Using CM10.1 with the brightness slider in the notification bar option, and I hate auto.. There are times indoors that there is something in the middle, but usually it's one or the other.