Yes we knew this
I think the conclusion was that even with the antenna detuning the iPhone 4 had better reception than the iPhone 3.
And if a bumper does not help then why not expose the antenna rather than sticking it just inside the plastic case like most smartphone do? Then iPhone 4 with a bumper is exactly like the iPhone 1-3 antenna placement wise.
My own experience with the iPhone 2 and iPhone 4 is that I get a little better reception with the iPhone 4. I use a bumper for glass protection but will probably remove it after a year or so when the phone isn't so shiny.