so does anyone have this unit and will buying it work better than the old ATI ATY,RadeonX1900, that doesnt work well with the new Leopard?
The X1900 works fine with Leopard, but because Leopard offloads more work to the GPU, the card gets exercised more. If you haven't cleaned the dust out your X1900's intake and fan assembly or taken further steps to cool it, you may see some instability.
I never had any freeze-ups in Tiger. Immediately after I upgraded to Leopard, I would get 1 or 2 freeze-ups a day, always when doing something graphics intensive like iTunes Visualizer, DVD playback, even activating Spaces. This tendency to lock up went away once I cleaned out my X1900 and applied some Arctic Silver thermal paste to the GPU/heat-sink interface.
In fact, for pro-apps like Final Cut, Motion, or Aperture the X1900 is quite a bit better than the 8800 (see the barefeats review). If and when updated drivers are released, the gap will probably narrow, but until then unless your X1900 is near death or you do a lot of 3D gaming, there is no reason to rush out and buy an 8800.