Not heard it, I've deduced it from those that have received their shipping info / had their device delivered.
I can't find a single instance where the bumper has been shipped. People who have ordered devices and the bumper as separate orders have the device shipped but not the bumper, and I can't find anyone who ordered the bumper and phone in the same order that has received shipping info.
This is from trawling through XDA threads as well as other forums, not a single shipped bumper that I can find in any country.