Harry, I have been more than happy with the quality of what Lightning Source produces for me. I put the quality of the binding on my books (they are "perfect bound" paperbacks) up against pretty much any I have seen from traditional publishers (and definitely better than some).
The cover image quality is very good to excellent (I chose a gloss laminate finish), though perhaps not up there with the very best of the trad-pubs I have - though in this case it may be the quality of image I supplied rather than printing that lets it down, I am still learning after all.
The text print-quality, too, is very good (I leave readers to assess the other qualities of the text
).
I was also very pleased with the paper quality. I chose a "creme" paper, which turned out to be very fine and crisp.
Lightning Source print at locations nearest to distribution, so my copies came from Australian printers. I checked my with friend in the UK and as far as I can tell the quality was just as good there.
The main negative things I have to say about my own print books have to do with my choices rather than anything Lightning Source did. I used a slightly smaller font, and relatively small margins, in order to keep the page count (and so the final cost) down as much as I could. I have had no complaints in that regard, but my own tastes would have preferred the font just a bit larger (I'm not as young as I was).