Looks like Apple has begun the process of refunding Apple Online Store bumper case orders. *MacRumors says:
Existing back-ordered bumper cases have also been processed for refund. We expect the process will continue over the next few days. Apple is also expected to provide a method for in-store purchasers to also receive a refund but has provided no details yet.
As part of their iPhone 4 "antennagate" press conference, Steve Jobs announced Apple would be giving away free cases, including Apple Bumpers, to every iPhone 4 customer as a way to make them happy and alleviate any concerns about reception issues.
Anyone else get their refund notice yet?