I used ImagePrint with my Epson 9600 and 9800 and liked it's output most of the time. The interface is kind of clunky, but the prints were good. With the 9600, it was the only way to get good black and white prints. I had a few images with weird shadow problems, but for the most part I was glad to use it.
With the Canon 8100 and now my 8300, and profiles I make myself, I don't miss ImagePrint at all as far as image quality goes. There is a convenience to throwing a bunch of pictures on a layout page without regard to resolution or image colorspace profile and having all the conversions done by the RIP, but I've adapted my workflow to accommodate not having that. The high price of ImagePrint was worth it initially for the image quality on those Epson printers, but I wouldn't pay it now as an alternative to the Canon.
I have no personal experience printing with the latest Epsons, with or without ImagePrint. Prints I've seen of others from the 9900 printing through the driver seem on a par with output from the Canon, so for me, the Canon's speed, cost and reliability make up a winning combination.