I just switched from the Iphone 4s to the Galaxy S3 and I will tell you the camera is really good. Not as good as the Iphone 4s but, you won't totally miss your Iphone camera.
I switched because I was bored after four years with the Iphone and so far I am loving my S3. After a week, the size of the phone did not bother me. It feels good in my hand. No regrets at all!
I was the 10th person in one day at the ATT store in my neighborhood, to trade their iphone in for the S3 (This was the day after the Iphone 5 was announced).