Update: According to these release notes, it looks like this rollout is full blown, not just a soak test. Happy updating!
As evidenced by the number of Android Central readers who sent us tips, along with posts by many of our forum members, it's clear that the soak test is rolling out. If you are one of the folks who have been invited to the soak test, be aware that the download for the Lollipop update is 652.5MB in size.
Thanks to our readers and forum members for the tips!