QImage produces excellent print results. I use it.
To its benefit: It's cheap, has great upscaling algorithms, is fast, ICC support, and allows some useful image tweaks prior to printing. Mike (developer) provides direct support via yahoo group, and he is quite responsive to genuine bugs.
To its detriment: Roll paper management is non-existent, the UI is at times wonky (although it is tolerable, there's a lot of frustration too), there's no gamut warning display, and running multiple customer jobs at once can result in annoying layouts.
As far as print quality, though, it's the best hundred bucks you can spend. What's that -- a single ink cartridge? Hardly a decision at all. Use it if you can.
-- woops, should have posted this in the other thread.