Hi Mark,
I have created a book in InDesign, printed by Blurb on Pro Line Pearl, hardcover, basically their top-mend product, and it is ...ok, I guess. The intended audience is happy/delighted, but personally I was disappointed by the lack of opaqueness of the paper - the outline of prints on the back side is quite clearly visible through the paper, without any backlighting (I'm sure there's a technical word for that, just can't remember it). Otherwise, fine, convenient, but really, far, far too expensive.
Regards
David