Factory reset won't always work if you replaced the system files on it (ex CM). In those cases, you might need to use Odin to flash back or flash the stock ROM through CWM. By the fact you said "reinstall AT&T version of ICS" it sounds like you might have done something like that?
Nope just have a bunch of free apps that are killing my perfomance and eating up mem..... Now I know not to download a bunch of crap free apps lol
You can just uninstall those apps to free up the space. No need to factory reset to simply remove the apps you don't want, unless you like to re-set up your accounts, email, social clients, etc.