Went to the local Apple Store last night and talked to a genius about the situation. Very friendly guy, and he logged a case for me, and pretty much said that at this point they have nothing they can do as they are waiting on word from engineering. Conveniently, I was there right when a worker was restocking the shelves with more bumpers, so for now I bought one.

Not really happy with the bumper though, as it's back to the iPhone 1 problem of very few 1/8th inch headphone plugs will seat fully. And of course, Apple again forgot to make even their own case work with docks much like on the iPad. I'll be returning it if some future firmware somehow resolves the issue of touching the bottom left.

Anandtech did a nice writeup with actual db signal numbers from the iPhone 4, 3GS and Nexus One (AT&T version).
http://www.anandtech.com/show/3794/the-iphone-4-review/2