I got the S3 last month and it fits fine in my front pocket. I was afraid it wouldn't fit so I wore my jeans with the smallest pockets when I got it and was pleasantly surprised. It probably helps that the pants are stretch. I don't use a case, but I did get a screen protector.
I don't use a purse so I only get pants that have decent pockets which isn't always easy to find. Hopefully the phones won't get bigger in the next year or two before I get another phone.