I reverted mine to ICS 4.0.4 today (not happy with the interface either). Here is how I did it...
-back up any data you don't want to lose from your tablet
-download the ICS firmware from the site of your choice and unzip it wherever you like
-download and install Odin3 (latest version I saw was 1.87, but I used 1.85) from the site of your choice on a Windows computer
-make sure all PC drivers for the tab are installed (they are installed by Kies)
-make sure Kies is not running
-turn off the tablet
-make sure the tablet is not plugged into the computer and has a good bit of battery left
-turn the tablet on into recovery mode by pressing and holding the up volume and the on/off button
-select factory reset and do it
-select reboot
-turn the tablet off again
-turn the tablet on into download mode by pressing and holding the down volume button and the on/off at the same time
-when it asks if you are sure you want to download, press up volume to say yes
-plug the tablet into the computer's USB port, and make sure it says "Added!" in the window
-check the PDA box in Odin
-click the PDA button and browse to the .md5 file you unzipped
-click Start in Odin
-when it finishes, the tablet should boot into ICS
-if the progress meter on the tablet and in the Odin window don't move for a long time, there might be a problem with the USB drivers... maybe try another usb port, or else reinstall the drivers
-if it hangs at the Samsung screen... I had that too, as I did all this initially without the factory wipe. After I did that and reflashed the rom, it started working again. If it does this even after the wipe, I would suggest trying the wipe and see if that works... if not, try flashing again too.
Be aware that there is always risk in flashing the firmware, and if things go wrong, I can't be responsible for that.
Good luck!