Homey, thanks for starting this thread
Regardless of whether or not people want to call this "spot-metering" or something else, the ability to meter the brightness to the point where your finger is pressing the screen is simply not working in my S3 or any of the S3's at various stores that I've tried.
This type of point-metering was what made my old HTC EVO camera so great. It is extremely frustrating not to be able to do this on my Galaxy S3.
Please, if anyone has an update as to why this isn't working and how we can fix it, please do tell!