It's available on the Tonga and Hawaii Chips (I know, it sucks for the Tahiti owners). Although, it make sense given the 512bit bus width of the Hawaii cards and the efficient memory of the Tonga cards.
Yup, the same as DSR. It's nothing special, you could do it before by setting a custom resolution. Many people also compare it to Super Sampling, which is not 100% correct, but the endresult and the performance impact are extremely similar.
I don't think they are going to. I think they are betting the power savings is gonna come from the smaller manufacturing process rather than a trim of the shaders. I think the biggest thing that hurts the 900 series is the narrow memory bus though. I don't think we will have to worry about bandwidth on the 3XX series!
I feel like some people may say AMD is just copying nVidia or playing catch up but I think those people will be in for quite a shock when the 3XX series drops.