Downloading this now, great work Vache! I love time-travel, this morning I woke up in Febuary and XDA has taken me to Mid-April, incredible
Will report back on how it goes.
I, too, have installed root keeper and activated root protection. I'm going to do a reboot with root keeper enabled before I reboot to flash update.zip. I've also disabled any programs/scripts that run at boot and/or requiring root to see if this might help at all.
EDIT: ICS Update applies fine, seems pretty stock, doesn't have any of the ring stuff Acer said is coming. Google Chrome from the Market works fine accept for crashing when opening the Settings menu. Root, however did not stick.