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Interface.... still pretty much the same. OpenGL preview compared to P6 is much better. PP reacts quicker and smoother then P6 does. Even when working on larger scenes, PP still reacts well, much better then P6 which tends to get slow.

Elaborate on "much better" please.  Is it just smoother and more responsive, or does it actually look better also?  I'd pay $400 just to get shadows and bump maps in the preview.