i just got a book back from Blurb and I have to say that while it's OK, I wasn't overly impressed. I used their top line Pro-Line paper and it was no better than what they had a number of years ago. It's equivalent to a good quality magazine, but certainly no where near as good as what AdoramaPix produces, which is more like printing using a high quality commercial inkjet photo printer on proper photo paper or prints form a wet chem process.
It also looks like Blurb may be doing some auto-correcting or hand correcting (incorrectly) since at least one image is a bit too bright. It's not an editing issue since the cover image is too bright but the exact same image on a full bleed page inside the book is spot on. The other issue using Blurb through LR is that there is no way to soft-proof because they use CMYK. So ... I have to take each image from LR into Photoshop, soft proof, save the adjusted image as a TIF or PSD or whatever, then bring it back into LR to finish the book. Pretty awful workflow IMO.
Binding quality is much better than AdoramaPix though, so I'm a bit torn as to which of the two I'd use again .... Better image quality or better book quality?