It is not worth a toss to upgrade if you are solely using it for photo processing.
The speed differencies in pure photoshopping (even 1-2Gb pics) are still constrained by performance of the programs,be it PS CS3,CS4 or CS5.
Some obscure filters might benefit from the speedups,but in general,dont bother.
You will gain much larger benefits by using keyboard shortcuts,reading the manual,taking a course,buying a wacom and learning properly automation than any computer upgrade.
Lightroom / Aperture will show some speedup (sometimes even significant if processing large libraries) with the newer machines but as a generalized you wouldnt notice difference in everyday work between MP 06,08,09 or 10
if doing day-to-day photoshopping for print.
That's good do know! That makes the $720 price difference (education store), easier to forego.
So CS5 and LR3 (I plan on upgrading) can't really use the extra turbo boost and two extra cores of the 3.33GHz Hexcore vs. the 3.2GHz Quad? If that's the case the I'll save some $$ and get the quad.
Can anyone else put thier two cents in on this?