How to Upgrade Your AT&T Samsung Galaxy S3 to Jelly Bean 4.1 (CyanogenMod10)... and Why?

I recently put up a short blog post on How to Root Your Samsung Galaxy S3... and Why?

Since then, I have installed Jelly Bean 4.1 (CyanogenMod 10) on my rooted Samsung Galaxy S3. The process went surprisingly quickly compared to installing Jelly Bean on the Samsung Captivate which I did a few months back. Here I will share the steps to get this done on your SGH-i747 AT&T Samsung Galaxy S3 as well.

Before I go through the steps though, I want to share the "why" on this upgrade.
The SGS3 is a new phone and retails for a hefty sum of dollars. Even with a 2-year contract it goes for up to $200 or so. Modifying it better be worth it, right? To me... it is. I already took the plunge by rooting the Samsung Galaxy S3 so I could use many of my favorite apps without limitation. In the end, I could only take the AT&T bloatware and Android 4.0 for so long. This is because I had been running Android 4.1 Jelly Bean on my Samsung Captive for months and had gotten spoiled by it. The ROM was CyanogenMod 10 which is one of the most reliable, supported, and tested ROMs available. There were some features I found myself missing while using the stock AT&T Android 4.0 on my new Samsung Galaxy S3. I missed these features enough to upgrade to a CyanogenMod 10 after owning the SGS3 for just over a week.

Some of the features/improvements from CyanogenMod10/Jelly Bean 4.1 that are must-haves for me include:

1. Google Now and voice search
2. Reboot into Recovery/Download mode and screenshot option from power menu
3. Detailed notifications for emails/texts which show extended previews, even for multiple email/text notifications
4. Shortcut icon 'groups' for the launcher
5. Improved interface for selecting which app to execute a specified action with
6. Improved interface for copying/pasting
7. Improved web browser with built-in ability to set the user agent
8. Ability to customize the notification LED
9. Battery/signal icons for the notification bar can include actual values, not just icons

So on to it... how to install Android 4.1 Jelly Bean (CyanogenMod 10) on your AT&T SGH-i747 Samsung Galaxy S3:

Keep in mind that you alone are responsible for the results here. I am only sharing my experiences, methods, and results for your information and curiosity. Once you root and/or flash a new ROM to your phone, you are risking 'bricking' your phone and at the least you will no longer be covered by warranty. This method is specific to the AT&T SGH-i747 model. Other carrier models will need to follow different steps.
Guide to revert your AT&T SGH-i747 Samsung Galaxy S3 back to stock
Official forum thread for the CyanogenMod 10 ROM for the SGH-i747 AT&T Samsung Galaxy S3

1. Follow the steps in my previous post: How to Root Your Samsung Galaxy S3... and Why? to root your SGS3 and install ClockWorkMod Recovery. Ensure you can boot into CWM recovery successfully and perform a backup.
2. Download the most recent 'stable' CyanogenMod 10 ROM (currently cm-10.0.0-d2att.zip from 11/13/2012) to your computer.
3. Download the most recent Google Apps package (currently gapps-jb-20121130-signed.zip from 11/30/2012) to your computer.
4. Connect your Galaxy S3 to your computer and transfer the 2 files above to your phone's internal memory. Backup your phone's files to your computer at this time if you prefer.
5. Boot into recovery (you can do this via ROM Manager, ROM Toolbox, or just by shutting down the phone and holding down the Volume Up, Home, and Power buttons together until it boots into recovery mode.
6. Use the volume keys to highlight 'Wipe data/factory reset' and press the power button to select that option. Select 'yes' to confirm.
7. Now go back to the main menu and select Install ZIP from SD card, then Choose ZIP from SD card
8. Find the CyanogenMod 10 zip file and select it, then 'yes' to confirm.
9. Once complete, go back to the main menu and select Install ZIP from SD card, then Choose ZIP from SD card again.
10. This time, find the Google Apps zip file and select it, then 'yes' to confirm.
11. Finally, go back to the main menu and select reboot to boot up your phone newly CyanogenMod 10 equipped Samsung Galaxy S3.
12. Setup your Google account(s), configure all the options/settings, and enjoy!