I display a 16 x 20 gallery wrap on the wall in my shop that was one of my first prints with QU and my new Epson 7900. It's a barn scene that was the result of a 60% crop from an original 1mb file, that while far from a pixel peepers ideal, really shows what QU is capable of.
It really impresses alot of people, and I still am amazed myself !  
 

I haven't done anything that radical, unless you count printing 5x7 from Sony Mavica files, but last year I couldn't pass up a local supplier's half-price sale on large prints.  Decided to treat myself to an 18x24.  Qimage's "Print to File" function turned my 2.8 mp original from my 8 mp p&s into a 19.8 mp file which I took to the supplier.  More than once I've taken the resulting print off the wall and handed it to someone to examine as closely as he wished.  Outstanding results from Qimage.

Want a laugh?  Google "camera resolution print size."  You'll turn up dozens of tables telling you that a photo of resolution X can only be printed thus-and-so large.  If you're a Qimage user, those guidelines are a joke.  I routinely printed outstanding 8x10s from my 4 mp Canon G2.  From my 8 mp Powershot Pro1 I printed my own stuff up to 13x19, and never hesitated to order 16x20 or larger...as long as I could prep the file with Qimage.

Probably.  I must admit that it's been years since I printed a low-res image.  And come to think of it, I printed those 5x7s from the Mavica with either Qimage Lite or Pro.  Have to dig them up and see what Ultimate can produce.

Just remembered these two shots (original, plus cropped version).  Perhaps the most severe crop I've printed with Qimage.  The 8x10 print looked great.