I just bought a scrapped Epson 9600. What strikes me is the incredible build toughness of the thing.
I have two Epson 7600's. I am picking up a 9600 from a friend next week. I am really looking forward to the ability to print 44".
These are great machines. As mentioned, they are true production machines built to keep going, all day, every day.
The 7600/9600 do a great job with the Ultrachrome K2 inks on matte paper. (I think that was the gist of the discussion above.)
When I bought my 7880, my dealer told me I would not see much difference between the 7600 and the 7880 on matte. Many others confirmed this.
There is no question, however, that the newer 7880/Z3100/3800 etc. have significant improvements in gamut, bronzing, gloss differential, and metamersim over the 7600/9600. I am still happy running Epson Premium Luster and even Epson Exhibition Fiber and Harman Gloss Ai prints off of the 7600 though.
Where these machines really shine, though, is if you start to get into alternative ink sets. They are the last of the wide format machines that are still relatively "open". That is, you can get into 3 different, detailed maintenance menus to do what ever you need to maintain/update the machines.
Resetting the maintenace tank, switching to dye inks, turning off the chip system for the inks so that you can use other cartridges, etc. You can also swap from Mastte Black to Photo Black pretty easily. Just swap carts and run out the ink in the black line only (the "South African" method. That should have been SOP on all the large format Epson machines!)
My dealer offered me $650 for my 7600 in trade on the 7880. I was going to do it. Then I thought that, for less than the cost of an Epson 2400, I had this **great** print engine for whatever inks I wanted to run in it. Much easier to refill the 220ml carts than bother with a CIS on the small systems too.
I have one 7600 with cheap dye inks that I use for large, cheap proofs (under $2 for a 24x36.) Another is running some B&W inks that I mixed for about $30 per liter (using Paul Roark's Carbon 6 mixing directions.)
I really love these machines! They are the last, great, open print engines for those of us who want to run our own ink sets. Still need to keep a newer machine around for production work for some clients though.