I have set Aurora to load at boot on my RGH 360 and it is just sitting on the Aurora splash screen with ...Scanning Title Updates in the bottom right of the screen. How long should this take? I have left it for 15mins and it still sits there. I can hit the guide button and it brings up the menu. I have tried going to the guide then file browser and selecting a different XEX but at that point the console hangs on the 'you will leave this game if you carry on' message.
it should only do it the first boot. it will backup all title updates as well, depending on how many you have and how fast your drive is, this may take a while.
if you really want to, you can change the setting in the db on a pc, using a SQLite tool (like SQLite Database Browser)
open the settings.db, select the SystemSettings Table and change TUScanAtBoot to 0
This might have a negative effect on TU management from aurora (you would have to redownload TU's you already had