I love these kinds of news:

In the next patch, and future patches, we are adding more shaders to help improve framerate on cards that support pixel shader model 1.4 and above. Also, we have not yet optimized some of our object rendering and UI rendering. Expect optimizations in these in the near future. Lastly, the client is not a full debug client, but does include a fair bit of debugging code (assertions and the like).

Its also been my experience that ATI cards run WoW better in Direct3D, and NVidia cards run WoW better in OpenGL. There are obviously exceptions to this, but it seems to be the case. Note that some graphical features dont work correctly (or at all) in OpenGL yet, but we will be addressing this in future beta patches.