QImage uses the Epson drivers so you don't really get any real differences with how your prints come out. You do get the ability to lay out print packages to make better use of your paper.
ImagePrint is a RIP. When you install ImagePrint, you have to tell it what printer you'll be using. Then, when you print through IP (it's not a photo editing application but it can do some simple things like crop, add borders and such) you use their custom profiles and their custom-designed drivers. You can download a trial version of the IP software for playing around with the interface but it won't allow you print using the trial version.
One benefit of using ImagePrint is their phatte black profiles. These special profiles allow you to load the matte black ink into the light, light black slot and leave it there. No more swapping and purging and wasting ink! You just download and install all the phatte black paper profiles you want to use and it knows when to use the matte or photo black ink based on the paper profile and paper type chosen for that print run.
When I want to print, I just tell ImagePrint what kind of paper (matte, glossy, luster, sheet, roll, etc) I'll be using and select the paper brand (Epson Luster 260, Red River Polar White Luster, etc). It's pretty slick.
The ImagePrint folks have custom profiled probably hundreds of papers for all sorts of printers. Their profile library is outstanding. I recently added a new paper and they didn't have any profiles for it. I emailed their customer support and within 2-3 days, they had added it to their library.
However, IP can do more that keep you from wasting ink purging back and forth. It can do print packages like QImage, it can resize your prints, you can even set it use less ink than normal to print (set it to use 95% ink rather than the usual 100%).
I don't waste prints anymore. It truly prints how I see it on my calibrated monitor. Before, I was using Miller's and I would get inconsistent results and would sometimes lose details in the shadows and have to get reprints done. Now, it's spot on every time even though my workflow is the same as before. The only time I have to reprint now is if I see something in the image that got missed when I was post processing it but it's
not because of the way the print looks on paper. My print quality has gone way up because I can control my printing so much better than before.
It's a robust application and takes a little bit of time to figure everything out but it wasn't that hard. Learning Photoshop was way harder. ImagePrint is expensive but I'm very happy with my results now. My purchase of the Epson 4880 and IP software was money well spent, IMHO.