Samsung Mobile uses a custom binary counter to keep track of any Modding of firmwares and kernels done by users of their phones. Any flashing of roms/kernels not signed by Samsung will trigger an increase in this counter which can be viewed by putting your phone into download mode.
Why is this important to you? This officially voids your warranty and tells warranty centers that you have broken your warranty which can give them rights to refuse or charge you for servicing your phone. Flashing a stock Samsung Note firmware signed by Samsung may also trigger the counter.
Previous Samsung mobiles have had the ability to have the counter reset to zero using a USB Jig. You cannot use the jig on the Note to wipe the counter.
To obtain root without tripping the counter you can follow this thread here: [Root] ATT Samsung Galaxy Note Root W/O Counter Trip
If you decide to flash anything, as always, make certain it is intended for your model of the Galaxy Note.
Edit: A CWM flashable zip has been released that will reset your counter to zero if you are running ICS. To flash it, download this att flashcounter reset - Minus and transfer it to the root of the /sdcard. Reboot into CWM and flash it. It can take a few seconds so be sure to be patient! Mad props to Braway for developing this without even owning a Note.