If anyone tries this on their 640 (particularly from 8.1), I'd love to hear your experience. I was thinking after the last build that the next one (i.e., what turned out to be 10166) might be the one I move my daily driver to. I figure if I brick it (upgrade fails and I can't revert), it's a $99 phone. But I'm always willing to let others try first. :grin: