I think in their eyes (AMD) the 6850 is supposed to be as fast as the 5850 and the 6870 as fast as the 5870. I think that's how they're trying to fool people into replacing their 5 series. And, with the prices sounding so keen for those kinds of speeds people may well rush out and buy.
As stand alone cards they will make no sense to 5 series owners right now. It seems that the 6870 has been designed and specced to take on the 1gb 460 though, and, offers a good Crossfire setup for the pennies. Shame about the overclock headroom but I guess they have to compete now (where as they didn't before) and so they're going to need to squeeze on the GPU a bit themselves.
If I hadn't gone 5770 Crossfire I would be strongly considering one of these cards right now. However with the huge price drop on the 470 I'm leaning toward green as long as they come up with a cooler and don't just keep knocking out toast 'r' ovens. Time will tell I guess.
Great review as ever. Sounds like you had some serious fun Tom