I've been able to use the new P800 for a while, and have just written up a lengthy review that I hope is of some interest.
It adds roll media support (that's me with a 10 foot print below) and a new ink set.
The printer I've got here is not quite a final production model (the case finish is a bit rough) but Epson tell me that it's essentially what will ship from a printmaking POV.
It's still here, so please just ask if there is something I've missed out (no... I can't take it apart!)