Although I don't have P7 as of yet (but they said it shipped!), I just had upgraded my computer from a 3.0 HT P4 to a 2.66 Core 2 Duo processor with new mother board.  In my other 3D applications, the speed increase in rendering an image is unbelievable.  A can render a 4000 x 4000 pixel image in Carrara and Daz Studio that would have taken all night long to render in about 10-20 minutes.  The savings in electric use alone should pay for the price of my upgrade, not to mention I can get to work post-processing my renders the save evening instead of having to wait till the next day.

I wanted the Quad processor, but it was out of my reach price wise right now.  In the future I'm sure they'll drop in price.