You left out some of the juicy tables?
At 2200MHz (4400Mhz DDR), the 4870 has a bandwidth of 140GB/s. That's about twice the bandwidth of a 3870.
50% more shaders at 50% higher clock combined with 100% more memory bandwidth than the 3870 = something good!
That is just the 4870. Times by two = 4870X2 = something very good?
Oh, release slated for June/July.
All the above ripped off from various places.