I got the email, went ahead and signed up for the soak test. I'm debating whether or not I want to go back to stock now and see what happens with this update. The survey mentioned that you should factory reset if you have rooted/modded anything, and that if you wait until the test is rolling out to wipe you will get kicked out of line and you will not get the update.
So, do you think it is worth risking losing root just to get the soak test? If there were any hope that this is the ICS update I would be all over it, but if its just another patch then I'm not sure. .901 has been going great for me so far.