It is a great program with a really, really crappy user interface.
Yes, this is it exactly. Designed by engineers for engineers, not for actual people. As an editor who has written more than 1,000 product reviews over a span of 30 years, I agree QU sports an incredibly un-intuitive and un-discoverable user interface.
I use QU all the time. It does a much better job at sharpening and handling detail than Photoshop, which requires explicit re-sizing for each different print dimension you want, or Lightroom which does an ok job.
I don't mind investing time to make a print, especially when doing my very large canvases or 30x40-inch prints. I spend many, many hours editing an image in Photoshop. For my clients, what matters is the results. QU gives me the best results. Yes, time is money, and invest a lot of time. But, I get paid for it.