Blurb have printed excellent results for me but the secret to getting the best quality from their service is NOT to use the consumer-level sRGB module in Lr.
Personally I have no issue with Blurb or the products they produce. They simply do not offer books with cover options/materials or page dimensions I prefer to offer my clients.
I do not wish to conform my workflow to Blurb in any software option ... I want Lr (Adobe) to allow me to fit my traditional vendors into the paradigm. It was a conscious decision to restrict the Book module to a Blurb only option. Something Adobe never did in the past. My vendors should not have to go to Adobe and request admission, Adobe should allow users to create custom page sizes ... Period!
Would InDesign ever have sold so well if output was restricted to a single vendor? Would Photoshop be the world's top graphics solution if it too were so restricted? Think also if the Develop module would only process NEF and not Cr2 ... if the Print Module would only work with HP printers and not Epson? ... or if the Web module would only export galleries that would work with IE and not Safari, Chrome or Firefox? See what I mean?
I have been creating books/albums in InDesign since long before Lr was ever developed. (Page Maker and Quark Xpress before that) I work with five different printers/binders that offer the cover materials, paper options and finished results that separate my efforts form my competition. I see no reason to conform to another single vendor and sacrifice my standards just to fit in with Adobe's idea of how the world should be. Whether I use Lr or ID ... if we all order our books from Blurb ... what good is it?
The main reason I would prefer to utilize album/book making in Lightroom ... is it offers a much more streamlined workflow in that users don't have to create all those exported derivative files to use in ID or elsewhere ... much less housecleaning involved to keep track of images used. Eventually, I will not be able to use Aperture for such tasks and don't want to return to all that duplication of effort in exporting a mountain of files each month to layout a book. Anyone who has done this in Aperture vs InDesign can tell you how much easier it is and how much less work it involves. (Before you ask ... there are several plugins for Aperture that you can export/order a book from some of the top wedding/portrait album printer/binders from around the world ... as well as export pages/spreads as tiff, jpeg or pdf using fully custom layouts with fully custom page sizes, margins and bleeds that could be used by nearly any vendor you choose as long as you set these variables to the proper requirements. Apple offered this without request from the start. No begging, pleading or excuses.)
I pay multiple licensing fees for Lr (both CC and perpetual) I don't think it's too much to ask, as long as I am making a contribution to the cause and Adobe is going to include a Book module, that they take into consideration how restrictive their design is for the Book module is and address this discrepancy appropriately.