OpenGL does look a lot nicer in P7, with a decent card.  I now have a Geforce 7300GT (not exactly top-of-the-line), but can view the document window with full hardware shading and the enhanced multilayer transparency options, which were too slow for my older Geforce 5700LE.  And you can control the resampling size of the preview textures.  Mine are set to four times larger than those in P6.  The level of detail is gratifying.