[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] cbski9:
I've had my AT&T SG3 for a few months now, and I rooted it right away and had a lot of fun "getting to know" Android (former iOS user). I constantly read these forums and found it daunting to decide whether to flash a custom ROM and which one. Finally, I bit the bullet. I did all the things I was supposed to... nandroid backup, titanium backup, clear cache, factory reset, flash, reboot, restore/reinstall individual apps & data.

I use my phone; it's not a toy, and I don't have more than one; so I was a bit nervous about it and took all the precautions. But, let me tell you that the CM10 ROM (cm-10-20120911-EXPERIMENTAL-d2att-M1) I installed blew my mind on what a positive difference it made. The phone is super fast, and various problems I had with the stock ROM (that came with the phone) has mysteriously gone away. I also feel liberated, because I did not realize how many features of the phone and OS were being "turned off" by the carrier and/or device manufacturer so as not to compete with their own apps/features.

I do realize this is still an "alpha" or "experimental" ROM, but I have to say I am extremely pleased so far. Reading about the "known bugs", I was almost expecting to have to flash back to stock. However, I have to say that many of the known bugs have not shown up on my device/carrier.

Here are the list of issues I had to overcome:

- ** The external SD card's file system was corrupted, but was recovered by putting the card in my windows PC and performing a chkdsk /r to repair the filesystem. Once repaired, all files were intact and I back them up to my computer, then formatted the card with GUIFormat from Ridgecrop to FAT32 with default allocation unit size. Something positive that I didn't expect was, when I used Quickformat to reformat from eFAT to FAT32, all the files were still intact. I didn't even have to recopy from the backup on my computer.

- Initially, I could not get the internet connection to work. I was connected to the network, but no internet (over carrier). I spent tons of time messing with the APN settings and trying all sorts of things. In the end, I just restored the default APNs and rebooted. So, once you go through the initial setup of the phone after flashing the ROM, you might just want to reboot once more for good measure!

- Using Titanium Backup, I restored many apps and their data, including SMS, MMS, etc. I made sure to check the option to "Migrate System Data" in hopes of making sure that the SMS/MMS data would convert and work properly from ICS to JB, and it did.

- ** The one important thing that could not be restored was the "accounts" data, so I had to re-setup my accounts and tell it what to sync for each account, default calendars, etc. This was by far the biggest inconvenience; however, I now have it setup to backup account settings to Google. I don't recall if that was available in ICS, but it is in JB; so I'm hoping that will make it much easier next time.

- Another thing was figuring out how to get Google Now assigned to a hardware button... you just go into Settings>System>Hardware keys, and the trick is to assign "voice search" to the "Menu key (long press)". I had seen all kinds of crazy workarounds and suggestions, but it's that simple.

- Once last quirk that I have NOT resolved yet, but the various system apps (Camera specifically) don't seem to save to the external SD card first and I can't find any setting to tell them to "prefer" the external SD card. If anyone knows how to to this in CM10 JB, please let me know. Not a big deal for now, because if the internal SD starts to fill up, I'll just copy to external SD.

I wish all this was documented somewhere because I spent a LOT of time dealing with these really simple quirks. Hindsight is 20/20! So, I thought I'd post to save you from sleepless hours after flashing from ICS to JB. I think "when/if" my carrier makes the the JB OTA update available, I may still stick with the CM10 ROM. I thought I'd miss various AT&T and Samsung apps like S-Voice or AT&T Hotspot, but I don't at all!

Some stock ROM quirks resolved:

- WIFI is faster and more reliable and seems to automatically switch between the two routers in my house based on signal strength!

- Carrier data is faster and signal strength appears to have improved. In the stock ICS, my phone seemed to get confused when switching back and forth from carrier data and wifi data

- The infamous audio crackling/popping/hissing is gone, and I love this Apollo player (very fast and nice UI)

- Everything about the phone is faster!

- The display/resolution seems clearer/crisper

- The auto brightness seems to work a lot better

- Account Sync and "Push" notifications seem to be much more reliable than before (maybe something to do with the WIFI/Carrier switching quirks in stock ICS)

- Can't say enough about AOSP Jelly Bean and how much better it is than Stock AT&T/Samsung ICS w/ TouchWiz

- The only stock app I miss is the Calendar! I think this is pretty "known" that the CM10 Calendar is basic.

Thanks for listening. Hopefully you'll find some useful info.