I always find KSR books have this initially intriguing and terribly interesting Hard SF aspect - in this case how a generation ship would work - but then I lose interest when that is all the book seems to involve. Problems occur somewhat randomly, solutions appear out of nowhere deus ex machina - and the characters and plot remain under developed and hard to sympathize with. I think in this case 3-4 good plots and stories could have been developed but were merged into one mammoth story covering hundreds of years.

And they abandon a viable planet because of a prion with no attempt to deal with it? this was never a serious option?