I forgot about the locked bootloader. While it may be possible to go back, the other poster is right. It very well could brick and isn't worth it.
You would be safer either figuring out foxfi or rooting and using Wifi tether
Sent from the nexus of the Android world, the SGS3.
We're not all as lucky as you s3 owners
lol
But yeah, the bootloader and kernel are different than what is on ics, so it wouldn't end well at all
Sent from my RAZR MAXXIMUS
Yeah way more involved and complicated.
It was even twice as hard as my htc and that was a pain before soff
Sent from the nexus of the Android world, the SGS3.
This is slightly off topic, but I'll bring it up because the reason I do it is avoid the same situation the OP finds himself in...
Unless there was absolutely no choice in the matter, I never buy a phone unless I know I can unlock the bootloader. When the S3 came out, I was definitely interested in it, but the bootloader was locked on the Verizon model, so I waited. Soon after, they announced there would be a dev model you could buy, which was fine with me because I pay full retail anyway...but page just kept saying "coming soon", so I waited. Then one fine day I stroll over to XDA and see the bootloader had been unlocked and I ordered by device that day. If a better phone had come along while I was waiting, I would have bought it, but only if I knew I could unlock the bootloader. I've become too accustomed to being able to control my device as I see fit and harness the full power of it as I need (plus have the ability to revert backwards when I screw stuff up) to ever go back now.
Again, sorry to throw that out there since it doesn't really help the OP or most folks here on this forum...but hopefully it can be something to consider the next time you're shopping for a new device, since it's one thing you generally won't see in product reviews.