I bought ImagePrint to work with my new 7880. I am now returning the RIP, after working with it extensively for a few weeks. Let me first say that it is a wonderful application. I have no problems with it. The built-in profiles were wonderful, the b/w printing was truly amazing, and the "ease" factor was very nice. And I thought I was going to use the Phatte option. Nevertheless, I find it overkill for my relatively low volume fine art printing. I don't need most of the functionality (layout, etc.) and I've decided I won't need the Phatte option. And the 7880 is capable of producing stunning prints on its own.
This is my first large format printer, so maybe I am too easily impressed. I have to admit that I don't care as much about screening, patterns, etc (even though I'm a graphic artist trained to obsess about such details). Even so, I found little difference when using the epson driver vs. RIP. Maybe if I inspected with a loupe I'd find something to worry about. I didn't do any testing - besides pressing my nose up to some Premium Luster prints. And 2880 printing through the Epson driver offered the finest quality, to my eye. If I can get stunning results out of the box, I'm off and running! Color and tonal capability are what I care about. The Epson profiles are good, but I am confident that I can get some outstanding results using custom profiles - which I may or may not have to tweak to equal the RIP output.
So, I'm getting my $1500 back ("few hundred"?!!), and buying some high end custom profiles for the few papers I've selected ... and plenty of ink and paper rolls. And I can "get by" with the decent output options of Lightroom.
And if RIPs really were only a few hundred, I'd certainly own ImagePrint. Or if I were doing mostly b/w printing, I'd own it - at full price.
I'd say, just test it for yourself. Even if you buy a RIP, you can always return it if you decide you don't need it - at least with the good people at Colorbyte.
By the way, the Onyx option is only available for Windows - as things stand now.