The last devkit we had info on (unfortunately not the final devkit EloquentM) used the RV770LE GPU. In fillrate numbers it does 2.3x what the Xbox 360 GPU can do theoretically, if clocked at 575 MHz (clockrates in the devkit are unclear, but I believe 500 MHz in an earlier revision was referred to as 'underclocked'?).
I'm just using what was spilled about the devkit and comparing the
available raw performance numbers. You can also extrapolate that that that GPU has ~3.8x the available shading power of the Xbox 360, or the same as roughly 429 GameCubes duct taped together (I love that number). Of course it's not the final GPU, but I think the final GPU will perform better rather than worse.
I made a post about this in the previous thread.