Contacting HTC by email will not result in any satisfaction. You need to call in and ask that your call be ESCALATED; that department does know about the problem and what is going on. They are still in the research-and-information gathering stage, so the more direct contact they have, the better/quicker the solution will be. But you are right to return the phone. I figure it may take another month or three to fix, and by then the "M7" will be released and it should be to the One X+ what the One X+ is to the Vivid.
Maybe the BT problem is a blessing in disguise?