It's just as well these things aren't defined in your weird little books then, SteelSix.
Re-badging = giving a different name to the same GPU silicon, AKA 8800GTS - 9800GT.
4890 uses a *different* GPU. Sure, there's no die shrink and apparently no changes to the quantity of shaders, but there are quite a lot of very important changes you can make to a silicon chip besides that. Are you aware of the concept of a die re-spin? And why is binning 'half bullshit'? That doesn't make any sense. In fact, apart from your closing comment, your whole post is meaningless. It's just ignorant.
There's a lot of "it looks the same so it must be an overclocked part" crap in here too - speculation is fine, but do you seriously think ATi would be stupid enough to release a newer card that is hotter than their already-very-hot model without addressing some of those issues? Step off your damn pedestals and have a little faith.
And what's this crap about people's card temperatures? I don't care how hot your GTX260 is at '40% fan speed', it's a totally different architecture to the 4890, with a different cooler and an entirely different approach to thermal design. ATi design their coolers to use the minimum fan speeds possible at idle whilst keeping the GPU below its rated maximum temperature (around 110 degrees C), in order to reduce idle noise levels. nVidia tend to produce less noise-sensitive designs, that's just their strategy. People keep shitting themselves over this because they think that a GPU that idles at 50-60 is somehow safer. Get some actual GPU return rate figures before you accuse a company's designs of being flawed, I'm sick of all this 'loads of people's cards failed' hand-waving. Do we even know why the cards that did fail failed? Was it the GPU, the memory, or the PCB? These are very, very important differences.
If you want to make efficiency comparisons, look at overall power draw; that's far more important because it tells you how much heat will have to be dissipated. The original 4870 drew less power at maximum than both the GTX280 and the GTX260, but more at idle. This is due to its use of GDDR5, as shown by the power draw difference between 4870 and 4850 (much more than the clock difference could account for). In other words, there's no obvious reason why a re-spun RV770 GPU on an improved 55nm manufacturing node and with a redesigned PCB can't perform well with reasonable thermals.
It's a speed-bump, it won't set the world on fire, it will be competitive, end of.