I believe that all of the discussion here is very valid, I will try to explain what I think a bit more:
First, the Epson 7900 makes lovely prints. The Epson print driver is quite capable and works extremely well. ImagePrint is absolutely not necessary and is in fact, very expensive. When MR says that with thge new printers RIP's can RIP, I respectfully disagree for the following reasons.
Where i am going with this is like many of you, I am highly critical of the visual quality of my prints. I can control the aesthetic composition, design, and feel of the image but I can't control the output given the parameters that are associated with inkjet printing much more than what is provided to me in the software. You see, I am a design professional by education. I am pretty illiterate when it comes to computer issues other then button pushing.
When I got the 7900, I was blown away by the ease with which I could get good looking prints. However, there was something missing. A subtlety that separates my mind from being drawn to the image as a visual experience vs looking at the image technically from a print quality viewpoint. I am torn between the two. The artist wants to ignore the technical side and the engineer wants to analyze the print image quality. This is a fight that I have on a continuing basis. I want the artist to win.
In order to asses the sublety of the images, I printed each image twice. Once using the Epson driver and once using IP8. I fine tuned the Epson driver output "as best as I could" using the paper manufacturers profiles. I am not into profiling as I have enough technical stuff to do in my profession, I don't want more to do in my art. Photography is an extension of the creative side and I really only want it to be art. Years ago I got into ink mixing and all of that stuff only to begin to despise all things photographic.
After printing and hanging the images, I spent several hours looking at the images. The IP results had that subtlety that I am speaking of. Perhaps this is arbitrary, perhaps it is just me, but the IP images just work. They are just better, they glow, they look better, they have better tonal range, they are smoother, they are more visually satifying. The best way I can describe this is that they are NOT harsh. Can I documet this technically or through rational analysis? No, and as I have mentioned I have no interest in doing so. Could I get the same results if I were to profile all of my papers and spend lot of time fine tuning? Maybe, but again for me ImagePrint just works. The images have wonderful shadow detail which is clean and distinct as well as smoother more uniform highlights.
If I were to place the two prints side by side and ask the lay person to explain the difference, chances are they might not see what I am speaking of. But for me, the difference is significant. It allows me to concentrate on the visual poetry of the image and experience the moment without letting the technical printing aspects get in the way.
With ImagePrint, erverthing else that can be a distraction just gets out of the way.